System and method for session sweeping between devices

ABSTRACT

An improved system and method are disclosed for peer-to-peer communications. In one example, the method enables an endpoint to sweep an ongoing communication session to another endpoint by transferring session information between the endpoints.

INCORPORATION BY REFERENCE

This application also incorporates by reference in their entirety U.S.Pat. No. 7,570,636, filed on Aug. 30, 2005, and entitled SYSTEM ANDMETHOD FOR TRAVERSING A NAT DEVICE FOR PEER-TO-PEER HYBRIDCOMMUNICATIONS, and U.S. patent application Ser. No. 12/705,925, filedon Feb. 15, 2010, and entitled SYSTEM AND METHOD FOR STRATEGIC ROUTINGIN A PEER-TO-PEER ENVIRONMENT.

BACKGROUND

Current packet-based communication networks may be generally dividedinto peer-to-peer networks and client/server networks. Traditionalpeer-to-peer networks support direct communication between variousendpoints without the use of an intermediary device (e.g., a host orserver). Each endpoint may initiate requests directly to other endpointsand respond to requests from other endpoints using credential andaddress information stored on each endpoint. However, becausetraditional peer-to-peer networks include the distribution and storageof endpoint information (e.g., addresses and credentials) throughout thenetwork on the various insecure endpoints, such networks inherently havean increased security risk. While a client/server model addresses thesecurity problem inherent in the peer-to-peer model by localizing thestorage of credentials and address information on a server, adisadvantage of client/server networks is that the server may be unableto adequately support the number of clients that are attempting tocommunicate with it. As all communications (even between two clients)must pass through the server, the server can rapidly become a bottleneckin the system.

Accordingly, what is needed are a system and method that addresses theseissues.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding, reference is now made to thefollowing description taken in conjunction with the accompanyingDrawings in which:

FIG. 1 is a simplified network diagram of one embodiment of a hybridpeer-to-peer system.

FIG. 2 a illustrates one embodiment of an access server architecturethat may be used within the system of FIG. 1.

FIG. 2 b illustrates one embodiment of an endpoint architecture that maybe used within the system of FIG. 1.

FIG. 2 c illustrates one embodiment of components within the endpointarchitecture of FIG. 2 b that may be used for cellular networkconnectivity.

FIG. 2 d illustrates a traditional softswitch configuration with twoendpoints.

FIG. 2 e illustrates a traditional softswitch configuration with threeendpoints and a media bridge.

FIG. 2 f illustrates one embodiment of the present disclosure with twoendpoints, each of which includes a softswitch.

FIG. 2 g illustrates one embodiment of the present disclosure with threeendpoints, each of which includes a softswitch.

FIG. 3 a is a sequence diagram illustrating the interaction of variouscomponents of FIG. 2 b when placing a call.

FIG. 3 b is a sequence diagram illustrating the interaction of variouscomponents of FIG. 2 b when receiving a call.

FIG. 4 is a sequence diagram illustrating an exemplary process by whichan endpoint of FIG. 1 may be authenticated and communicate with anotherendpoint.

FIG. 5 is a sequence diagram illustrating an exemplary process by whichan endpoint of FIG. 1 may determine the status of another endpoint.

FIG. 6 is a sequence diagram illustrating an exemplary process by whichan access server of FIG. 1 may aid an endpoint in establishingcommunications with another endpoint.

FIG. 7 is a sequence diagram illustrating an exemplary process by whichan endpoint of FIG. 1 may request that it be added to the buddy list ofanother endpoint that is currently online.

FIG. 8 is a sequence diagram illustrating an exemplary process by whichan endpoint of FIG. 1 may request that it be added to the buddy list ofanother endpoint that is currently offline.

FIG. 9 is a sequence diagram illustrating an exemplary process by whichan endpoint of FIG. 1 may request that it be added to the buddy list ofanother endpoint that is currently offline before it too goes offline.

FIG. 10 is a simplified diagram of another embodiment of a peer-to-peersystem that includes a stateless reflector that may aid an endpoint intraversing a NAT device to communicate with another endpoint.

FIG. 11 is a table illustrating various NAT types and illustrativeembodiments of processes that may be used to traverse each NAT typewithin the system of FIG. 10.

FIG. 12 is a sequence diagram illustrating one embodiment of a processfrom the table of FIG. 11 in greater detail.

FIG. 13 illustrates one embodiment of a modified packet that may be usedwithin the process of FIG. 12.

FIGS. 14-18 are sequence diagrams that each illustrate an embodiment ofa process from the table of FIG. 11 in greater detail.

FIGS. 19A and 19B are simplified diagrams of another embodiment of apeer-to-peer system that includes multiple possible routes betweenendpoints.

FIG. 20 is a sequence diagram illustrating one embodiment of a processthat may be executed by endpoints within the system of FIGS. 19A and19B.

FIG. 21 is a sequence diagram illustrating one embodiment of steps fromthe sequence diagram of FIG. 20 in greater detail.

FIG. 22 is a flow chart illustrating one embodiment of a method that maybe executed by an endpoint within the system of FIGS. 19A and 19B.

FIGS. 23A and 23B are simplified diagrams of another embodiment of apeer-to-peer system that includes a tunneling server and multiplepossible routes between endpoints.

FIG. 24 is a sequence diagram illustrating one embodiment of a processthat may be executed by endpoints within the system of FIGS. 23A and23B.

FIG. 25 is a simplified diagram of another embodiment of a peer-to-peerenvironment in which an endpoint may sweep an existing session toanother endpoint.

FIG. 26 is a sequence diagram illustrating one embodiment of a messagesequence that may occur when a session is being swept between endpointswithin the environment of FIG. 25.

FIG. 27 is a flow chart illustrating one embodiment of a method that maybe executed by an endpoint to which the session is being swept withinthe environment of FIG. 25.

FIG. 28 is a flow chart illustrating one embodiment of a method that maybe executed by an endpoint from which the session is being swept withinthe environment of FIG. 25.

FIG. 29 is a flow chart illustrating one embodiment of a method that maybe executed by an endpoint that is involved in a session that is beingswept between two other endpoints within the environment of FIG. 25.

FIG. 30 is a simplified diagram of one embodiment of a computer systemthat may be used in embodiments of the present disclosure.

DETAILED DESCRIPTION

The present disclosure is directed to a system and method forpeer-to-peer hybrid communications. It is understood that the followingdisclosure provides many different embodiments or examples. Specificexamples of components and arrangements are described below to simplifythe present disclosure. These are, of course, merely examples and arenot intended to be limiting. In addition, the present disclosure mayrepeat reference numerals and/or letters in the various examples. Thisrepetition is for the purpose of simplicity and clarity and does not initself dictate a relationship between the various embodiments and/orconfigurations discussed.

Referring to FIG. 1, one embodiment of a peer-to-peer hybrid system 100is illustrated. The system 100 includes an access server 102 that iscoupled to endpoints 104 and 106 via a packet network 108. Communicationbetween the access server 102, endpoint 104, and endpoint 106 isaccomplished using predefined and publicly available (i.e.,non-proprietary) communication standards or protocols (e.g., thosedefined by the Internet Engineering Task Force (IETF) or theInternational Telecommunications Union-Telecommunications StandardSector (ITU-T)). For example, signaling communications (e.g., sessionsetup, management, and teardown) may use a protocol such as the SessionInitiation Protocol (SIP), while actual data traffic may be communicatedusing a protocol such as the Real-time Transport Protocol (RTP). As willbe seen in the following examples, the use of standard protocols forcommunication enables the endpoints 104 and 106 to communicate with anydevice that uses the same standards. The communications may include, butare not limited to, voice calls, instant messages, audio and video,emails, and any other type of resource transfer, where a resourcerepresents any digital data. In the following description, media trafficis generally based on the user datagram protocol (UDP), whileauthentication is based on the transmission control protocol/internetprotocol (TCP/IP). However, it is understood that these are used forpurposes of example and that other protocols may be used in addition toor instead of UDP and TCP/IP.

Connections between the access server 102, endpoint 104, and endpoint106 may include wireline and/or wireless communication channels. In thefollowing description, it is understood that the term “direct” meansthat there is no endpoint or access server in the communicationchannel(s) between the endpoints 104 and 106, or between either endpointand the access server. Accordingly, the access server 102, endpoint 104,and endpoint 106 are directly connected even if other devices (e.g.,routers, firewalls, and other network elements) are positioned betweenthem. In addition, connections to endpoints, locations, or services maybe subscription based, with an endpoint only having access if theendpoint has a current subscription. Furthermore, the followingdescription may use the terms “user” and “endpoint” interchangeably,although it is understood that a user may be using any of a plurality ofendpoints. Accordingly, if an endpoint logs in to the network, it isunderstood that the user is logging in via the endpoint and that theendpoint represents the user on the network using the user's identity.

The access server 102 stores profile information for a user, a sessiontable to track what users are currently online, and a routing table thatmatches the address of an endpoint to each online user. The profileinformation includes a “buddy list” for each user that identifies otherusers (“buddies”) that have previously agreed to communicate with theuser. Online users on the buddy list will show up when a user logs in,and buddies who log in later will directly notify the user that they areonline (as described with respect to FIG. 4). The access server 102provides the relevant profile information and routing table to each ofthe endpoints 104 and 106 so that the endpoints can communicate directlywith one another. Accordingly, in the present embodiment, one functionof the access server 102 is to serve as a storage location forinformation needed by an endpoint in order to communicate with otherendpoints and as a temporary storage location for requests, voicemails,etc., as will be described later in greater detail.

With additional reference to FIG. 2 a, one embodiment of an architecture200 for the access server 102 of FIG. 1 is illustrated. The architecture200 includes functionality that may be provided by hardware and/orsoftware, and that may be combined into a single hardware platform ordistributed among multiple hardware platforms. For purposes ofillustration, the access server in the following examples is describedas a single device, but it is understood that the term applies equallyto any type of environment (including a distributed environment) inwhich at least a portion of the functionality attributed to the accessserver is present.

In the present example, the architecture includes web services 202(e.g., based on functionality provided by XML, SOAP, .NET, MONO), webserver 204 (using, for example, Apache or IIS), and database 206 (using,for example, mySQL or SQLServer) for storing and retrieving routingtables 208, profiles 210, and one or more session tables 212.Functionality for a STUN (Simple Traversal of UDP through NATs (NetworkAddress Translation)) server 214 is also present in the architecture200. As is known, STUN is a protocol for assisting devices that arebehind a NAT firewall or router with their packet routing. Thearchitecture 200 may also include a redirect server 216 for handlingrequests originating outside of the system 100. One or both of the STUNserver 214 and redirect server 216 may be incorporated into the accessserver 102 or may be a standalone device. In the present embodiment,both the server 204 and the redirect server 216 are coupled to thedatabase 206.

Referring to FIG. 2 b, one embodiment of an architecture 250 for theendpoint 104 (which may be similar or identical to the endpoint 106) ofFIG. 1 is illustrated. It is understood that that term “endpoint” mayrefer to many different devices having some or all of the describedfunctionality, including a computer, a VoIP telephone, a personaldigital assistant, a cellular phone, or any other device having an IPstack upon which the needed protocols may be run. Such devices generallyinclude a network interface, a controller coupled to the networkinterface, a memory coupled to the controller, and instructionsexecutable by the controller and stored in the memory for performing thefunctions described in the present application. Data needed by anendpoint may also be stored in the memory. The architecture 250 includesan endpoint engine 252 positioned between a graphical user interface(GUI) 254 and an operating system 256. The GUI 254 provides user accessto the endpoint engine 252, while the operating system 256 providesunderlying functionality, as is known to those of skill in the art.

The endpoint engine 252 may include multiple components and layers thatsupport the functionality required to perform the operations of theendpoint 104. For example, the endpoint engine 252 includes a softswitch258, a management layer 260, an encryption/decryption module 262, afeature layer 264, a protocol layer 266, a speech-to-text engine 268, atext-to-speech engine 270, a language conversion engine 272, anout-of-network connectivity module 274, a connection from other networksmodule 276, a p-commerce (e.g., peer commerce) engine 278 that includesa p-commerce agent and a p-commerce broker, and a cellular networkinterface module 280.

Each of these components/layers may be further divided into multiplemodules. For example, the softswitch 258 includes a call control module,an instant messaging (IM) control module, a resource control module, aCALEA (Communications Assistance to Law Enforcement Act) agent, a mediacontrol module, a peer control module, a signaling agent, a fax controlmodule, and a routing module.

The management layer 260 includes modules for presence (i.e., networkpresence), peer management (detecting peers and notifying peers of beingonline), firewall management (navigation and management), mediamanagement, resource management, profile management, authentication,roaming, fax management, and media playback/recording management.

The encryption/decryption module 262 provides encryption for outgoingpackets and decryption for incoming packets. In the present example, theencryption/decryption module 262 provides application level encryptionat the source, rather than at the network. However, it is understoodthat the encryption/decryption module 262 may provide encryption at thenetwork in some embodiments.

The feature layer 264 provides support for various features such asvoice, video, IM, data, voicemail, file transfer, file sharing, class 5features, short message service (SMS), interactive voice response (IVR),faxes, and other resources. The protocol layer 266 includes protocolssupported by the endpoint, including SIP, HTTP, HTTPS, STUN, RTP, SRTP,and ICMP. It is understood that these are examples only, and that feweror more protocols may be supported.

The speech-to-text engine 268 converts speech received by the endpoint(e.g., via a microphone or network) into text, the text-to-speech engine270 converts text received by the endpoint into speech (e.g., for outputvia a speaker), and the language conversion engine 272 may be configuredto convert inbound or outbound information (text or speech) from onelanguage to another language. The out-of-network connectivity module 274may be used to handle connections between the endpoint and externaldevices (as described with respect to FIG. 12), and the connection fromother networks module 276 handles incoming connection attempts fromexternal devices. The cellular network interface module 280 may be usedto interact with a wireless network.

With additional reference to FIG. 2 c, the cellular network interfacemodule 280 is illustrated in greater detail. Although not shown in FIG.2 b, the softswitch 258 of the endpoint architecture 250 includes acellular network interface for communication with the cellular networkinterface module 280. In addition, the cellular network interface module280 includes various components such as a call control module, asignaling agent, a media manager, a protocol stack, and a deviceinterface. It is noted that these components may correspond to layerswithin the endpoint architecture 250 and may be incorporated directlyinto the endpoint architecture in some embodiments.

Referring to FIG. 2 d, a traditional softswitch architecture isillustrated with two endpoints 282 and 284, neither of which includes asoftswitch. In the present example, an external softswitch 286 maintainsa first signaling leg (dotted line) with the endpoint 282 and a secondsignaling leg (dotted line) with the endpoint 284. The softswitch 286links the two legs to pass signaling information between the endpoints282 and 284. Media traffic (solid lines) may be transferred between theendpoints 282 and 284 via a media gateway 287.

With additional reference to FIG. 2 e, the traditional softswitcharchitecture of FIG. 2 d is illustrated with a third endpoint 288 thatalso does not include a softswitch. The external softswitch 286 nowmaintains a third signaling leg (dotted line) with the endpoint 288. Inthe present example, a conference call is underway. However, as none ofthe endpoints includes a softswitch, a media bridge 290 connected toeach endpoint is needed for media traffic. Accordingly, each endpointhas at most two concurrent connections—one with the softswitch forsignaling and another with the media bridge for media traffic.

Referring to FIG. 2 f, in one embodiment, unlike the traditionalarchitecture of FIGS. 2 d and 2 e, two endpoints (e.g., the endpoints104 and 106 of FIG. 1) each include a softswitch (e.g., the softswitch258 of FIG. 2 b). Each endpoint is able to establish and maintain bothsignaling and media traffic connections (both virtual and physical legs)with the other endpoint. Accordingly, no external softswitch is needed,as this model uses a distributed softswitch method to handlecommunications directly between the endpoints.

With additional reference to FIG. 2 g, the endpoints 104 and 106 areillustrated with another endpoint 292 that also contains a softswitch.In this example, a conference call is underway with the endpoint 104acting as the host. To accomplish this, the softswitch contained in theendpoint 104 enables the endpoint 104 to support direct signaling andmedia traffic connections with the endpoint 292. The endpoint 104 canthen forward media traffic from the endpoint 106 to the endpoint 292 andvice versa. Accordingly, the endpoint 104 may support multipleconnections to multiple endpoints and, as in FIG. 2 f, no externalsoftswitch is needed.

Referring again to FIG. 2 b, in operation, the softswitch 258 usesfunctionality provided by underlying layers to handle connections withother endpoints and the access server 102, and to handle services neededby the endpoint 104. For example, as is described below in greaterdetail with respect to FIGS. 3 a and 3 b, incoming and outgoing callsmay utilize multiple components within the endpoint architecture 250.

Referring to FIG. 3 a, a sequence diagram 300 illustrates an exemplaryprocess by which the endpoint 104 may initiate a call to the endpoint106 using various components of the architecture 250. Prior to step 302,a user (not shown) initiates a call via the GUI 254. In step 302, theGUI 254 passes a message to the call control module (of the softswitch258) to make the call. The call control module contacts the peer controlmodule (softswitch 258) in step 304, which detects the peer (if notalready done), goes to the routing table (softswitch 258) for therouting information, and performs similar operations. It is understoodthat not all interactions are illustrated. For example, the peer controlmodule may utilize the peer management module (of the management layer260) for the peer detection. The call control module then identifies aroute for the call in step 306, and sends message to the SIP protocollayer (of the protocol layer 266) to make the call in step 308. In step310, the outbound message is encrypted (using the encryption/decryptionmodule 262) and the message is sent to the network via the OS 256 instep 312.

After the message is sent and prior to receiving a response, the callcontrol module instructs the media control module (softswitch 258) toestablish the needed near-end media in step 314. The media controlmodule passes the instruction to the media manager (of the managementlayer 260) in step 316, which handles the establishment of the near-endmedia.

With additional reference to FIG. 3 b, the message sent by the endpoint104 in step 312 (FIG. 3 a) is received by the endpoint 106 and passedfrom the OS to the SIP protocol layer in step 352. The message isdecrypted in step 354 and the call is offered to the call control modulein step 356. The call control module notifies the GUI of an incomingcall in step 358 and the GUI receives input identifying whether the callis accepted or rejected (e.g., by a user) in step 360. In the presentexample, the call is accepted and the GUI passes the acceptance to thecall control module in step 362. The call control module contacts thepeer control module in step 364, which identifies a route to the callingendpoint and returns the route to the call control module in step 366.In steps 368 and 370, the call control module informs the SIP protocollayer that the call has been accepted and the message is encrypted usingthe encryption/decryption module. The acceptance message is then sent tothe network via the OS in step 372.

In the present example, after the call control module passes theacceptance message to the SIP protocol layer, other steps may occur toprepare the endpoint 106 for the call. For example, the call controlmodule instructs the media control module to establish near-end media instep 374, and the media control module instructs the media manager tostart listening to incoming media in step 376. The call control modulealso instructs the media control module to establish far-end media (step378), and the media control module instructs the media manager to starttransmitting audio in step 380.

Returning to FIG. 3 a, the message sent by the endpoint 106 (step 372)is received by the OS and passed on to the SIP protocol layer in step318 and decrypted in step 320. The message (indicating that the call hasbeen accepted) is passed to the call control module in step 322 and fromthere to the GUI in step 324. The call control module then instructs themedia control module to establish far-end media in step 326, and themedia control module instructs the media manager to start transmittingaudio in step 328.

The following figures are sequence diagrams that illustrate variousexemplary functions and operations by which the access server 102 andthe endpoints 104 and 106 may communicate. It is understood that thesediagrams are not exhaustive and that various steps may be excluded fromthe diagrams to clarify the aspect being described.

Referring to FIG. 4 (and using the endpoint 104 as an example), asequence diagram 400 illustrates an exemplary process by which theendpoint 104 may authenticate with the access server 102 and thencommunicate with the endpoint 106. As will be described, afterauthentication, all communication (both signaling and media traffic)between the endpoints 104 and 106 occurs directly without anyintervention by the access server 102. In the present example, it isunderstood that neither endpoint is online at the beginning of thesequence, and that the endpoints 104 and 106 are “buddies.” As describedabove, buddies are endpoints that have both previously agreed tocommunicate with one another.

In step 402, the endpoint 104 sends a registration and/or authenticationrequest message to the access server 102. If the endpoint 104 is notregistered with the access server 102, the access server will receivethe registration request (e.g., user ID, password, and email address)and will create a profile for the endpoint (not shown). The user ID andpassword will then be used to authenticate the endpoint 104 during laterlogins. It is understood that the user ID and password may enable theuser to authenticate from any endpoint, rather than only the endpoint104.

Upon authentication, the access server 102 updates a session tableresiding on the server to indicate that the user ID currently associatedwith the endpoint 104 is online. The access server 102 also retrieves abuddy list associated with the user ID currently used by the endpoint104 and identifies which of the buddies (if any) are online using thesession table. As the endpoint 106 is currently offline, the buddy listwill reflect this status. The access server 102 then sends the profileinformation (e.g., the buddy list) and a routing table to the endpoint104 in step 404. The routing table contains address information foronline members of the buddy list. It is understood that steps 402 and404 represent a make and break connection that is broken after theendpoint 104 receives the profile information and routing table.

In steps 406 and 408, the endpoint 106 and access server 102 repeatsteps 402 and 404 as described for the endpoint 104. However, becausethe endpoint 104 is online when the endpoint 106 is authenticated, theprofile information sent to the endpoint 106 will reflect the onlinestatus of the endpoint 104 and the routing table will identify how todirectly contact it. Accordingly, in step 410, the endpoint 106 sends amessage directly to the endpoint 104 to notify the endpoint 104 that theendpoint 106 is now online. This also provides the endpoint 104 with theaddress information needed to communicate directly with the endpoint106. In step 412, one or more communication sessions may be establisheddirectly between the endpoints 104 and 106.

Referring to FIG. 5, a sequence diagram 500 illustrates an exemplaryprocess by which authentication of an endpoint (e.g., the endpoint 104)may occur. In addition, after authentication, the endpoint 104 maydetermine whether it can communicate with the endpoint 106. In thepresent example, the endpoint 106 is online when the sequence begins.

In step 502, the endpoint 104 sends a request to the STUN server 214 ofFIG. 2. As is known, the STUN server determines an outbound IP address(e.g., the external address of a device (i.e., a firewall, router, etc.)behind which the endpoint 104 is located), an external port, and a typeof NAT used by the device. The type of NAT may be, for example, fullcone, restricted cone, port restricted cone, or symmetric, each of whichis discussed later in greater detail with respect to FIG. 10. The STUNserver 214 sends a STUN response back to the endpoint 104 in step 504with the collected information about the endpoint 104.

In step 506, the endpoint 104 sends an authentication request to theaccess server 102. The request contains the information about endpoint104 received from the STUN server 214. In step 508, the access server102 responds to the request by sending the relevant profile and routingtable to the endpoint 104. The profile contains the external IP address,port, and NAT type for each of the buddies that are online.

In step 510, the endpoint 104 sends a message to notify the endpoint 106of its online status (as the endpoint 106 is already online) and, instep 512, the endpoint 104 waits for a response. After the expiration ofa timeout period within which no response is received from the endpoint106, the endpoint 104 will change the status of the endpoint 106 from“online” (as indicated by the downloaded profile information) to“unreachable.” The status of a buddy may be indicated on a visual buddylist by the color of an icon associated with each buddy. For example,when logging in, online buddies may be denoted by a blue icon andoffline buddies may be denoted by a red icon. If a response to a notifymessage is received for a buddy, the icon representing that buddy may bechanged from blue to green to denote the buddy's online status. If noresponse is received, the icon remains blue to indicate that the buddyis unreachable. Although not shown, a message sent from the endpoint 106and received by the endpoint 104 after step 514 would indicate that theendpoint 106 is now reachable and would cause the endpoint 104 to changethe status of the endpoint 106 to online. Similarly, if the endpoint 104later sends a message to the endpoint 106 and receives a response, thenthe endpoint 104 would change the status of the endpoint 106 to online.

It is understood that other embodiments may implement alternate NATtraversal techniques. For example, a single payload technique may beused in which TCP/IP packets are used to traverse a UDP restrictedfirewall or router. Another example includes the use of a double payloadin which a UDP packet is inserted into a TCP/IP packet. Furthermore, itis understood that protocols other than STUN may be used. For example,protocols such as Internet Connectivity Establishment (ICE) or TraversalUsing Relay NAT (TURN) may be used.

Referring to FIG. 6, a sequence diagram 600 illustrates an exemplaryprocess by which the access server 102 may aid the endpoint 104 inestablishing communications with the endpoint 106 (which is a buddy).After rendering aid, the access server 102 is no longer involved and theendpoints may communicate directly. In the present example, the endpoint106 is behind a NAT device that will only let a message in (towards theendpoint 106) if the endpoint 106 has sent a message out. Unless thisprocess is bypassed, the endpoint 104 will be unable to connect to theendpoint 106. For example, the endpoint 104 will be unable to notify theendpoint 106 that it is now online.

In step 602, the endpoint 106 sends a request to the STUN server 214 ofFIG. 2. As described previously, the STUN server determines an outboundIP address, an external port, and a type of NAT for the endpoint 106.The STUN server 214 sends a STUN response back to the endpoint 106 instep 604 with the collected information about the endpoint 106. In step606, the endpoint 106 sends an authentication request to the accessserver 102. The request contains the information about endpoint 106received from the STUN server 214. In step 608, the access server 102responds to the request by sending the relevant profile and routingtable to the endpoint 106. In the present example, the access server 102identifies the NAT type associated with the endpoint 106 as being a typethat requires an outbound packet to be sent before an inbound packet isallowed to enter. Accordingly, the access server 102 instructs theendpoint 106 to send periodic messages to the access server 102 toestablish and maintain a pinhole through the NAT device. For example,the endpoint 106 may send a message prior to the timeout period of theNAT device in order to reset the timeout period. In this manner, thepinhole may be kept open indefinitely.

In steps 612 and 614, the endpoint 104 sends a STUN request to the STUNserver 214 and the STUN server responds as previously described. In step616, the endpoint 104 sends an authentication request to the accessserver 102. The access server 102 retrieves the buddy list for theendpoint 104 and identifies the endpoint 106 as being associated with aNAT type that will block communications from the endpoint 104.Accordingly, in step 618, the access server 102 sends an assist messageto the endpoint 106. The assist message instructs the endpoint 106 tosend a message to the endpoint 104, which opens a pinhole in the NATdevice for the endpoint 104. For security purposes, as the access server102 has the STUN information for the endpoint 104, the pinhole opened bythe endpoint 106 may be specifically limited to the endpoint associatedwith the STUN information. Furthermore, the access server 102 may notrequest such a pinhole for an endpoint that is not on the buddy list ofthe endpoint 106.

The access server 104 sends the profile and routing table to theendpoint 104 in step 620. In step 622, the endpoint 106 sends a message(e.g., a ping packet) to the endpoint 104. The endpoint 104 may thenrespond to the message and notify the endpoint 106 that it is nowonline. If the endpoint 106 does not receive a reply from the endpoint104 within a predefined period of time, it may close the pinhole (whichmay occur simply by not sending another message and letting the pinholetime out). Accordingly, the difficulty presented by the NAT device maybe overcome using the assist message, and communications between the twoendpoints may then occur without intervention by the access server 102.

Referring to FIG. 7, a sequence diagram 700 illustrates an exemplaryprocess by which the endpoint 106 may request that it be added to theendpoint 104's buddy list. In the present example, the endpoints 104 and106 both remain online during the entire process.

In step 702, the endpoint 104 sends a registration and/or authenticationrequest message to the access server 102 as described previously. Uponauthentication, the access server 102 updates a session table residingon the server to indicate that the user ID currently associated with theendpoint 104 is online. The access server 102 also retrieves a buddylist associated with the user ID currently used by the endpoint 104 andidentifies which of the buddies (if any) are online using the sessiontable. As the endpoint 106 is not currently on the buddy list, it willnot be present. The access server 102 then sends the profile informationand a routing table to the endpoint 104 in step 704.

In steps 706 and 708, the endpoint 106 and access server 102 repeatsteps 702 and 704 as described for the endpoint 104. The profileinformation sent by the access server 102 to the endpoint 106 will notinclude the endpoint 104 because the two endpoints are not buddies.

In step 710, the endpoint 106 sends a message to the access server 102requesting that the endpoint 104 be added to its buddy list. The accessserver 102 determines that the endpoint 104 is online (e.g., using thesession table) in step 712 and sends the address for the endpoint 104 tothe endpoint 106 in step 714. In step 716, the endpoint 106 sends amessage directly to the endpoint 104 requesting that the endpoint 106 beadded to its buddy list. The endpoint 104 responds to the endpoint 106in step 718 with either permission or a denial, and the endpoint 104also updates the access server 102 with the response in step 720. Forexample, if the response grants permission, then the endpoint 104informs the access server 102 so that the access server can modify theprofile of both endpoints to reflect the new relationship. It isunderstood that various other actions may be taken. For example, if theendpoint 104 denies the request, then the access server 102 may notrespond to another request by the endpoint 106 (with respect to theendpoint 104) until a period of time has elapsed.

It is understood that many different operations may be performed withrespect to a buddy list. For example, buddies may be deleted,blocked/unblocked, buddy status may be updated, and a buddy profile maybe updated. For block/unblock, as well as status and profile updates, amessage is first sent to the access server 102 by the endpointrequesting the action (e.g., the endpoint 104). Following the accessserver 102 update, the endpoint 104 sends a message to the peer beingaffected by the action (e.g., the endpoint 106).

Buddy deletion may be handled as follows. If the user of the endpoint104 wants to delete a contact on a buddy list currently associated withthe online endpoint 106, the endpoint 104 will first notify the accessserver 102 that the buddy is being deleted. The access server 102 thenupdates the profile of both users so that neither buddy list shows theother user as a buddy. Note that, in this instance, a unilateral actionby one user will alter the profile of the other user. The endpoint 104then sends a message directly to the endpoint 106 to remove the buddy(the user of the endpoint 104) from the buddy list of the user ofendpoint 106 in real time. Accordingly, even though the user is onlineat endpoint 106, the user of the endpoint 104 will be removed from thebuddy list of the endpoint 106

Referring to FIG. 8, a sequence diagram 800 illustrates an exemplaryprocess by which the endpoint 106 may request that it be added to theendpoint 104's buddy list. In the present example, the endpoint 104 isnot online until after the endpoint 106 has made its request.

In step 802, the endpoint 106 sends a registration and/or authenticationrequest message to the access server 102 as described previously. Uponauthentication, the access server 102 updates a session table residingon the server to indicate that the user ID currently associated with theendpoint 106 is online. The access server 102 also retrieves a buddylist associated with the user ID currently used by the endpoint 106 andidentifies which of the buddies (if any) are online using the sessiontable. The access server 102 then sends the profile information and arouting table to the endpoint 106 in step 804.

In step 806, the endpoint 106 sends a message to the access server 102requesting that the endpoint 104 be added to its buddy list. The accessserver 102 determines that the endpoint 104 is offline in step 808 andtemporarily stores the request message in step 810. In steps 812 and814, the endpoint 104 and access server 102 repeat steps 802 and 804 asdescribed for the endpoint 106. However, when the access server 102sends the profile information and routing table to the endpoint 104, italso sends the request by the endpoint 106 (including addressinformation for the endpoint 106).

In step 816, the endpoint 104 responds directly to the endpoint 106 witheither permission or a denial. The endpoint 104 then updates the accessserver 102 with the result of the response in step 818 and alsoinstructs the access server to delete the temporarily stored request.

Referring to FIG. 9, a sequence diagram 900 illustrates an exemplaryprocess by which the endpoint 106 may request that it be added to theendpoint 104's buddy list. In the present example, the endpoint 104 isnot online until after the endpoint 106 has made its request, and theendpoint 106 is not online to receive the response by endpoint 104.

In step 902, the endpoint 106 sends a registration and/or authenticationrequest message to the access server 102 as described previously. Uponauthentication, the access server 102 updates a session table residingon the server to indicate that the user ID currently associated with theendpoint 106 is online. The access server 102 also retrieves a buddylist associated with the user ID currently used by the endpoint 106 andidentifies which of the buddies (if any) are online using the sessiontable. The access server 102 then sends the profile information and arouting table to the endpoint 106 in step 904.

In step 906, the endpoint 106 sends a message to the access server 102requesting that the endpoint 104 be added to its buddy list. The accessserver 102 determines that the endpoint 104 is offline in step 908 andtemporarily stores the request message in step 910. In step 912, theendpoint 106 notifies the access server 102 that it is going offline.

In steps 914 and 916, the endpoint 104 and access server 102 repeatsteps 902 and 904 as described for the endpoint 106. However, when theaccess server 102 sends the profile information and routing table to theendpoint 104, it also sends the request by the endpoint 106. Endpoint104 sends its response to the access server 102 in step 918 and alsoinstructs the access server to delete the temporarily stored request.After the endpoint 106's next authentication process, its profileinformation will include endpoint 104 as a buddy (assuming the endpoint104 granted permission).

Referring to FIG. 10, in one embodiment, a system 1000 includes astateless reflector 1002 and two endpoints 104 and 106, such as theendpoints 104 and 106 described with respect to the preceding figures.In the present example, each of the endpoints 104 and 106 are behind adevice 1004, 1006, respectively, that monitors and regulatescommunication with its respective endpoint. Each device 1004, 1006 inthe present example is a firewall having NAT technology. As describedpreviously, a NAT device may present an obstacle in establishing apeer-to-peer connection because it may not allow unsolicited messages(e.g., it may require a packet to be sent out through the NAT devicebefore allowing a packet in). For example, the NAT device 1006positioned between the endpoint 106 and network 108 may only let amessage in (towards the endpoint 106) if the endpoint 106 has sent amessage out. Unless the NAT device's status is shifted from notsoliciting messages from the endpoint 104 to soliciting messages fromthe endpoint 104, the endpoint 104 will be unable to connect to theendpoint 106. For example, the endpoint 104 will be unable to notify theendpoint 106 that it is now online.

As will be described below in greater detail, the stateless reflector1002 is configured to receive one or more packets from an endpoint andreflect the packet to another endpoint after modifying informationwithin the packet. This reflection process enables the endpoints 104 and106 to communicate regardless of the presence and type of the NATdevices 1004 and 1006. The stateless reflector 1002 is stateless becausestate information (e.g., information relating to how an endpoint is toconnect with other endpoints) is stored by the endpoints, as describedpreviously. Accordingly, the stateless reflector 1002 processes headerinformation contained within a packet without access to otherinformation about the network or endpoints, such as the database 206 ofFIG. 2 a. Although only one stateless reflector 1002 is illustrated inFIG. 10, it is understood that multiple stateless reflectors may beprovided, and that the endpoints 104 and 106 may each use a differentstateless reflector. For example, an endpoint may be configured to use aparticular stateless reflector or may select a stateless reflector basedon location, NAT type, etc.

Although each endpoint 104, 106 is shown with a separate NAT device1004, 1006, it is understood that multiple endpoints may be connected tothe network 108 via a single NAT device. For example, a LAN may accessthe network 108 via a single NAT device, and all communications betweenthe endpoints connected to the LAN and the network 108 must pass throughthe NAT device. However, communications between the endpoints within theLAN itself may occur directly, as previously described, because theendpoints are not communicating through the NAT device. Furthermore, ifone of the endpoints 104 or 106 does not have a NAT device, thencommunications with that endpoint may occur directly as described aboveeven if the endpoints are not in the same network.

Each NAT device 1004 and 1006 includes an internal IP address (on theside coupled to the endpoint 104 for the NAT device 1004 and the sidecoupled to the endpoint 106 for the NAT device 1006) and an external IPaddress (on the side coupled to the network 108 for both NAT devices).Each connection is also associated with an internal port and an externalport. Therefore, each connection includes both internal IP address/portinformation and external IP address/port information.

Generally, a NAT device may be defined as full cone, restricted cone,port restricted cone, or symmetric. A full cone NAT is one where allrequests from the same internal IP address and port are mapped to thesame external IP address and port. Therefore, any external host can senda packet to the internal host by sending a packet to the mapped externaladdress.

A restricted cone NAT is one where all requests from the same internalIP address and port are mapped to the same external IP address and port.Unlike a full cone NAT, an external host can send a packet to theinternal host only if the internal host has previously sent a packet tothe external host's IP address.

A port restricted cone NAT is like a restricted cone NAT, but therestriction includes port numbers. More specifically, an external hostcan send a packet with source IP address X and source port P to theinternal host only if the internal host has previously sent a packet tothe external host at IP address X and port P.

A symmetric NAT is one where all requests from the same internal IPaddress and port to a specific destination IP address and port aremapped to the same external IP address and port. If the same host sendsa packet with the same source address and port, but to a differentdestination, a different mapping is used. Only the external host thatreceives a packet can send a UDP packet back to the internal host.

Referring to FIG. 11, a table 1100 illustrates one embodiment of acommunication structure that may be used to traverse one or both of theNAT devices 1004 and 1006 of FIG. 10. The table 1100 provides fivepossible types for the NAT devices 1004 and 1006: no NAT, full cone,restricted cone, port restricted cone, and symmetric. It is understoodthat “no NAT” may indicate that no device is there, that a device isthere but does not include NAT functionality, or that a device is thereand any NAT functionality within the device has been disabled. Either ofthe NAT devices 1004 and 1006 may be on the originating side of thecommunication or on the terminating side. For purposes of convenience,the endpoint 104 is the originating endpoint and the endpoint 106 is theterminating endpoint, and the NAT device 1004 is the originating NATdevice and the NAT device 1006 is the terminating NAT device. It isunderstood that the terms “endpoint” and “NAT device” may be usedinterchangeably in some situations. For example, sending a packet to theendpoint 106 generally involves sending a packet to the NAT device 1006,which then forwards the packet to the endpoint 106 after performing thenetwork address translation. However, the following discussion maysimply refer to sending a packet to the endpoint 106 and it will beunderstood that the packet must traverse the NAT device 1006.

As illustrated by the table 1100, there are twenty-five possiblepairings of NAT types and establishing communication between differentNAT types may require different steps. For purposes of convenience,these twenty-five pairings may be grouped based on the required steps.For example, if the originating NAT type is no NAT, full cone,restricted cone, or port restricted cone, then the originating NAT canestablish communication directly with a terminating NAT type of eitherno NAT or full cone.

If the originating NAT type is no NAT or full cone, then the originatingNAT can establish communications with a terminating NAT type of eitherrestricted cone or port restricted cone only after using the statelessreflector 1002 to reflect a packet. This process is described below withrespect to FIG. 12.

Referring to FIG. 12, the endpoint 104 wants to inform the endpoint 106,which is already logged on, that the endpoint 104 has logged on. The NATdevice 1004 is either a no NAT or a full cone type and the NAT device1006 is either a restricted cone or a port restricted cone type.Accordingly, the endpoint 104 wants to send a message to the endpoint106, but has not received a message from the endpoint 106 that wouldallow the endpoint 104 to traverse the NAT device 1006.

Although not shown in FIG. 12, prior to or during authentication, theendpoints 104 and 106 both sent a request to a STUN server (e.g., theSTUN server 214 of FIG. 2) (not shown in FIG. 10). The STUN serverdetermined an outbound IP address, an external port, and a type of NATfor the endpoints 104 and 106 (in this example, for the NAT devices 1004and 1006). The STUN server 214 then sent a STUN response back to theendpoints 104 and 106 with the collected information. The endpoints 104and 106 then sent an authentication request to an access server (e.g.,the access server 102 of FIG. 1) (not shown in FIG. 10). The requestcontains the information about endpoints 104 and 106 received from theSTUN server 214. The access server 102 responds to the requests bysending the relevant profile and routing table to the endpoints 104 and106. In addition, each NAT device 1004 and 1006 may have a pinhole tothe STUN server 214.

In the present example, the NAT device 1004 has an external address/portof 1.1.1.1:1111 and the NAT device 1006 has an external address/port of2.2.2.2:2222. The STUN server 214 has an address/port of 3.3.3.3:3333and the stateless reflector has an address/port of 4.4.4.4:4444. It isunderstood that the STUN server and/or stateless reflector 1002 may havemultiple addresses/ports.

Referring to FIG. 12 and with additional reference to FIG. 13, in step1202, the endpoint 104 sends a packet to the stateless reflector 1002.The packet contains header information identifying the source as theendpoint 104 (or rather, the external IP address of the NAT device 1004)and the destination as the stateless reflector 1002. The packet alsocontains custom or supplemental header information identifying thesource as the STUN server 214 and the destination as the endpoint 106.Accordingly, the IP/UDP header of the packet sent from the endpoint 104(via the NAT device 1004) identifies its source as 1.1.1.1:1111 and itsdestination as 4.4.4.4:4444.

In step 1204, the stateless reflector 1002 modifies the packet header byreplacing the IP/UDP header with the source and destination from thecustom header. In the present example, the stateless reflector 1002 willmodify the IP/UDP header to identify the packet's source as 3.3.3.3:3333and its destination as 2.2.2.2:2222. Identifying the packet's source asthe STUN server 214 enables the stateless reflector 1002 to send thepacket through the pinhole in the NAT device 1006 that was created whenthe endpoint 106 logged on. After modifying the header, the statelessreflector 1002 sends the packet to the endpoint 106 via the NAT device1006 in step 1206.

In step 1208, the endpoint 106 sends an acknowledgement (e.g., a 200 OK)directly to the endpoint 104. The address of the endpoint 104 iscontained within the payload of the packet. The endpoint 106 is able tosend the acknowledgement directly because the NAT device 1004 is eithera no NAT or a full cone type. Because the endpoint 106 has opened apinhole through the restricted or port restricted NAT device 1006 to theendpoint 104 by sending a message to the endpoint 104, the endpoint 104is now able to communicate directly with the endpoint 106, as indicatedby step 1210.

Referring again to table 1100 of FIG. 11, if the originating NAT type iseither a no NAT type or a full cone type, then the originating NAT canestablish communications with a terminating NAT type that is symmetriconly after using the stateless reflector 1002 to reflect a packet andthen performing a port capture. This process is described below withrespect to FIG. 14.

Referring to FIG. 14, steps 1402, 1404, 1406, and 1408 are similar tothe reflection process described with respect to FIG. 12, and will notbe described in detail in the present example. Because the terminatingNAT type is symmetric, the originating NAT needs the port of theterminating NAT in order to send packets through the NAT device 1006.Accordingly, in step 1410, the endpoint 104 will capture the externalport used by the NAT device 1006 to send the acknowledgement in step1408. This port, along with the address of the NAT device 1006, may thenbe used when communicating with the endpoint 106, as indicated by step1412.

Referring again to table 1100 of FIG. 11, if the originating NAT type iseither a restricted cone type or a port restricted cone type, then theoriginating NAT can establish communications with a terminating NAT typethat is either restricted or port restricted by using a fake packet andthen using the stateless reflector 1002 to reflect a packet. Thisprocess is described below with respect to FIG. 15.

Referring to FIG. 15, in step 1502, the endpoint 104 sends a fake packetto the endpoint 106. Because the originating NAT type is a restrictedcone type or a port restricted cone type, the fake packet opens apinhole to the terminating NAT that will allow a response from theterminating NAT to penetrate the originating NAT. After sending the fakepacket, the sequence 1500 proceeds with steps 1504, 1506, 1508, and1510, which are similar to the reflection process described with respectto FIG. 12, and will not be described in detail in the present example.The endpoints 104 and 106 may then communicate directly, as indicated bystep 1512.

Referring again to table 1100 of FIG. 11, if the originating NAT type isa symmetric type, then the originating NAT can establish communicationswith a terminating NAT type that is either no NAT or full cone after aport capture occurs. This process is described below with respect toFIG. 16.

Referring to FIG. 16, in step 1602, the endpoint 104 (symmetric NATtype) sends a message to the endpoint 106. In step 1604, the endpoint106 captures the external port used by the NAT device 1004 in sendingthe message. This port, along with the address of the NAT device 1004,may then be used when communicating with the endpoint 104 directly, asindicated by step 1606.

Referring again to table 1100 of FIG. 11, if the originating NAT type isa restricted cone type, then the originating NAT can establishcommunications with a terminating NAT type that is symmetric by using afake packet, reflecting a packet using the stateless reflector 1002, andthen performing a port capture. This process is described below withrespect to FIG. 17.

Referring to FIG. 17, in step 1702, the endpoint 104 sends a fake packetto the endpoint 106. Because the originating NAT type is a restrictedcone type, the fake packet opens a pinhole to the terminating NAT thatwill allow a response from the terminating NAT to penetrate theoriginating NAT. After sending the fake packet, the sequence 1700proceeds with steps 1704, 1706, 1708, and 1710, which are similar to thereflection process described with respect to FIG. 12, and will not bedescribed in detail in the present example. In step 1712, the endpoint104 captures the external port used by the NAT device 1006 in sendingthe acknowledgement in step 1710. This port, along with the address ofthe NAT device 1006, may then be used when communicating with theendpoint 106 directly, as indicated by step 1714.

Referring again to table 1100 of FIG. 11, if the originating NAT type isa symmetric type, then the originating NAT can establish communicationswith a terminating NAT type that is a restricted cone type by using areflect, a fake packet, and a port capture. This process is describedbelow with respect to FIG. 18.

Referring to FIG. 18, steps 1802, 1804, and 1806 are similar to thereflection process described with respect to FIG. 12, and will not bedescribed in detail in the present example. In step 1808, in response tothe reflected message from the endpoint 104, the endpoint 106 sends afake packet to the endpoint 104. Because the terminating NAT type is arestricted cone type, the fake packet opens a pinhole to the endpoint104 to allow messages from the endpoint 104 to traverse the NAT device1006. Accordingly, in step 1810, the endpoint 104 can send the nextmessage directly to the endpoint 106 through the pinhole. In step 1812,the endpoint 106 captures the external port used by the NAT device 1004to send the message in step 1810. This port, along with the address ofthe NAT device 1004, may then be used by the endpoint 106 whencommunicating directly with the endpoint 104, as indicated by step 1814.

Referring again to table 1100 of FIG. 11, if the originating NAT type isa symmetric type and the terminating NAT type is a port restricted cone,or if the originating NAT type is a port restricted cone and theterminating NAT type is symmetric, then all signaling between the twoNAT devices is relayed via the stateless reflector 1002, while media istransferred via peer-to-peer, as described previously. If both theoriginating and terminating NAT types are symmetric, then all signalingand media are relayed via the stateless reflector 1002.

Accordingly, the peer-to-peer communications described herein may beachieved regardless of the NAT type that may be used by an endpoint. Thestateless reflector 1002 need not know the information for each client,but instead reflects various packets based on information containedwithin the packet that is to be reflected. Both the custom header andpayload may be encrypted for security purposes. However, the statelessreflector 1002 may only be able to decrypt the custom header and thepayload itself may only be decrypted by the terminating endpoint. Thisenables the stateless reflector 1002 to perform the reflectionfunctionality while maintaining the security of the payload itself. Asdescribed above, not all processes for traversing a NAT device may usethe stateless reflector 1002.

Referring to FIGS. 19A and 19B, in another embodiment, a peer-to-peerenvironment 1900 includes the two endpoints 104 and 106, the two NATdevices 1004 and 1006, and the stateless reflector 1002 of FIG. 10, andanother endpoint 1901. Also illustrated are three possible routesbetween endpoints: a private (pr) route 1902, a public (pu) route 1904,and a reflected (rl) route 1906. FIG. 19A illustrates the routes 1902,1904, and 1906 between the endpoint 104 and the endpoint 1901, and FIG.19B illustrates the routes between the endpoint 104 and the endpoint106. As will be discussed below in detail, the endpoints 104, 106, and1901 may contain logic that allows one of the three routes 1902, 1904,and 1906 to be selected in a dynamic and flexible manner rather thanrelying on the rule-based system described above.

A rule-based system may be fairly inflexible, as such a system generallyhas a clear set of rules that are defined for various NAT situations andthe current relationship between the two endpoints is handled accordingto those rules. Network configuration changes and other modificationsmay require revisions to the rules, which is not convenient and mayprevent the endpoints from communicating until the rules are revised.Accordingly, in some embodiments, the flexibility described below mayenable the endpoints 104, 106, and 1901 to adapt to new networkconfigurations without requiring updated rules as would be required in astrictly rule-based system. In still other embodiments, the logic withinthe endpoints 104, 106, and 1901 may be updated to handle new networkconfigurations, which also provides flexibility not found in strictlyrule-based systems.

Each endpoint 104, 106, and 1901 may include one or more virtualinterfaces for communication with other endpoints. In the presentexample, there are three virtual interfaces including a private virtualinterface corresponding to the private route 1902, a public virtualinterface corresponding to the public route 1904, and a relay virtualinterface corresponding to the relay route 1906. It is understood thatthe term “virtual interface” is used only for purposes of description toclarify that there are multiple possible routes. Accordingly, the term“virtual interface” need not denote separate physical network interfaceson an endpoint, but may use a single physical network interface.

As described above, each endpoint 104, 106, and 1901 is generallyassociated with two IP address/port pairs. The first IP address/portpair may be the local (i.e., private) IP address/port information thatrepresents each of the endpoints 104, 106, and 1901 in the network thatis “inside” the corresponding NAT device 1004 or 1006. For example, thefirst IP address/port pair for the endpoint 104 may be the physicaladdress assigned to the endpoint 104 by the corresponding NAT device1004. This first IP address/port pair corresponds to the private virtualinterface and may provide access via the private route to the endpoint104 by endpoints in the same local network (e.g., the endpoint 1901).The second IP address/port pair may be the public IP address/portinformation that represents each of the endpoints 104, 106, and 1901 inthe network that is “outside” the corresponding NAT device 1004 or 1006.For example, the second IP address/port pair for the endpoint 104 may bethe address that is returned to the endpoint 104 by the STUN server aspreviously described (e.g., the NAT's external IP address/port pairassigned to the endpoint 104). This second IP address/port pair for theendpoint 104 corresponds to the public virtual interface and may provideaccess via the public route to the endpoint 104 by endpoints both insideand outside the endpoint 104's local network. Each endpoint 104, 106,and 1901 is also aware of the address information of the reflector 1002as described in previous embodiments, which corresponds to the relayvirtual interface of the endpoints. The relay route may be used in(5,4), (4,5), and/or (5,5) conditions according to the table of FIG. 11,where one endpoint must send a packet first, but is unable to do sobecause the other endpoint must send a packet first.

Referring to FIG. 20, a sequence diagram illustrates one embodiment of amessage sequence 2000 that may occur between the endpoints 104 and 1901of FIG. 19A when identifying which of the routes (i.e., the privateroute 1902, the public route 1904, and the relay route 1906) will beused for communications. In the present example, the endpoints 104 and1901 are in a local (i.e., private) network such as an Enterprisenetwork, a local area network (LAN), a virtual LAN (VLAN), or a homenetwork. This local network is isolated from the public network by theNAT device 1004 or a similar network component. Although shown as asingle NAT device, it is understood that the NAT device 1004 may be aseparate NAT device for each of the endpoints 104 and 1901. In contrast,the endpoint 106 is in a separate network that is only accessible by theendpoints 104 and 1901 via a public network that forms all or part ofthe packet network 108.

The present example uses a SIP messaging model over UDP, and soaccommodates the transaction-based SIP model within connection-less UDPmessaging. Because UDP is not transaction based, certain messagehandling processes may be used to conform to SIP standards, such asdiscarding multiple messages when the SIP model expects a messagebelonging to a specific transaction. However, it is understood that thesequence 2000 may be implemented using many different messaging models.In the present example, neither endpoint is online at the beginning ofthe sequence and the endpoints 104 and 1901 are “buddies.” As describedabove, buddies are endpoints that have both previously agreed tocommunicate with one another.

In steps 2002 and 2006, the endpoints 104 and 1901, respectively, sendSTUN requests to obtain their corresponding public IP address/port pairs(NATIP, NATPort). In the present example, the reflector 1002 is servingas a STUN server, but it is understood that the STUN server may beseparate from the reflector. The reflector 1002 responds to the STUNrequests with the public IP address and port information for each of theendpoints 104 and 1901 in steps 2004 and 2008, respectively.

As the two endpoints 104 and 1901 are not logged in when the presentexample begins, they must both authenticate with the access server 102.In step 2010, the endpoint 104 sends an authentication request to theaccess server 102 with its private and public IP address/port pairs. Instep 2012, the access server 102 responds to the authentication requestand, as described previously, returns information that includes theprivate and public IP addresses of any buddy endpoints that arecurrently logged in. However, as the endpoint 1901 has not yet loggedin, the information received by the endpoint 104 from the access server102 will not include any address information for the endpoint 1901.

In step 2014, the endpoint 1901 sends an authentication request to theaccess server 102 with its private and public IP address/port pairs. Instep 2016, the access server 102 responds to the authentication requestand, as described previously, returns information that includes theprivate and public IP addresses of any buddy endpoints that arecurrently logged in. As the endpoint 104 is currently logged in, theinformation received by the endpoint 1901 from the access server 102will include the private and public address information for the endpoint104. Although not shown, the endpoint 1901 may then send a message tothe endpoint 104 informing the endpoint 104 that the endpoint 1901 iscurrently online. This message may contain the private and publicaddress information of the endpoint 1901. The message may be sent viathe three different routes as described below with respect to latermessaging, or may be sent via one or more selected routes. For example,the message may only be relayed (i.e., sent via the relay route) due tothe high chance of success of that route.

At this point, the endpoint 104 wants to establish a communicationsession with the endpoint 1901, but does not know which of the threeroutes (i.e., pr, pu, and rl) should be used. In the previouslydescribed rule-based system, the endpoint 1901 would publish its NATinformation, which enables the endpoint 104 to determine how toestablish a connection. However, in the present example, suchinformation is not published and the endpoint 104 does not know whetherthe endpoint 1901 is in the same private network as the endpoint 104,whether the endpoint 1901 is only accessible via a public network,whether the endpoint 1901 is behind a NAT device, or, if the endpoint1901 is behind a NAT device, the settings of the NAT device (full cone,port restricted, etc.). Accordingly, the endpoint 104 needs todynamically determine which of the three routes to use with the endpoint1901.

Accordingly, in step 2018, the endpoint 104 interacts with the endpoint1901 to determine which of the three routes should be used to sendmessages to the endpoint 1901. Similarly, in step 2020, the endpoint1901 interacts with the endpoint 104 to determine which of the threeroutes should be used to send messages to the endpoint 104, which maynot be the same route as that used by the endpoint 104 to send messagesto the endpoint 1901. Steps 2018 and 2020 are illustrated in greaterdetail below with respect to FIG. 21. In step 2022, the two endpointscommunicate via the determined route(s).

Referring to FIG. 21, a sequence diagram illustrates one embodiment of amessage sequence 2100 that may occur during steps 2018 and 2020 of FIG.20 in order to determine which of the routes are to be used. Theendpoint 104 may keep a table containing each buddy that is online andthe route to be used for that buddy. For example, when the route isunknown, the table may have the information shown in Table 1 below:

TABLE 1 Buddy Endpoint Route (send-receive) 1901 unk-unk X X X X

The endpoint 104 (which is the originating endpoint in the presentexample) sends out three presence messages in steps 2102, 2104, and2106. As the current example uses SIP messaging transported via UDP, themessage is a SIP INFO message. More specifically, in step 2102, theendpoint 104 sends a SIP INFO message to the private IP address/portpair of the endpoint 1901 (i.e., via the private route) with anidentifier such as a ‘pr’ tag to indicate the route. In step 2104, theendpoint 104 sends a SIP INFO message to the public (NAT) IPaddress/port pair of the endpoint 1901 (i.e., via the public route) withan identifier such as a ‘pu’ tag to indicate the route. In step 2106,the endpoint 104 sends a SIP INFO message to the endpoint 1901 via thereflector 1002 (i.e., via the relay route) with an identifier such as an‘rl’ tag to indicate the route, which is reflected to the endpoint 1901in step 2108.

The order in which the messages are sent may vary, but the order followsa hierarchy of desired routes in the present embodiment that places theprivate route first (i.e., most desirable), the public route next, andthe relay route last (i.e., least desirable). However, it is understoodthat the order in which the messages are sent may vary or, if theendpoint 104 is capable of sending multiple messages simultaneously, themessages may be sent at the same time.

The present example assumes that the endpoint 1901 receives one or moreof the messages sent in steps 2102, 2104, and 2106. If more than onemessage is received, the endpoint 1901 may respond only to the first onereceived. So, for example, if the message sent via the private route isreceived before the messages sent via the public and relay routes, theendpoint 1901 will respond only to the private route message and thelater messages will be ignored. This reduces network traffic andprovides for SIP compliance as the endpoint 104 (from a SIP perspective)expects to receive a single 200 OK message in response to its SIP INFOmessage. Furthermore, the response message may be sent back along thesame route as the presence message to which the response is directed. Soa response to the private route message will be sent back along theprivate route. Accordingly, only one of steps 2110A, 2110B, and 2110C-1may occur in the present example. Step 2110C-2 is dependent on theoccurrence of step 2110C-1 because the response message will not bereflected unless the relay route is used.

The response message returned by the endpoint 1901 is a SIP 200 OKmessage that may include the tag extracted from the received INFOmessage to identify which of the routes was successful (e.g., whichroute carried the message that was received first). For purposes ofexample, the private route was successful and the table may then beupdated as shown in Table 2 below:

TABLE 2 Buddy Endpoint Route (send-receive) 1901 pr-unk X X X X

It is noted that since the private route is successful, the twoendpoints 104 and 1901 are in the same private network.

It is understood that the response message (e.g., the SIP 200 OK) maynever be received by the endpoint 104. For example, the private routemay not be available from the endpoint 1901 to the endpoint 104 due tonetwork configuration settings. Accordingly, if the SIP 200 OK is notreceived by the endpoint 104, the endpoint 104 may execute aretransmission process that resends the presence messages along thethree routes. The resending may occur a set number of times, for a setperiod of time, or until some other limit is reached. For example, thefirst set of presence messages may be sent 0.5 seconds after the initialmessages are sent, the second set of messages may be sent one secondafter that, and each additional set of messages may be sent at timeperiods that are double the previous delay until a total of seven setsof messages are sent. At this time, the endpoint 104 may stop sendingmessages. If a response is received during the retransmission process,the endpoint 104 will stop retransmitting. However, the response messagewill generally be received by the endpoint 104.

The outbound SIP INFO messages and the received SIP 200 OK messageinform the endpoint 104 of which route to use when sendingcommunications to the endpoint 1901. However, this route may not work inreverse. In other words, just because the endpoint 104 can reach theendpoint 1901 via the private route (to continue the example), it doesnot necessarily follow that the endpoint 1901 can reach the endpoint 104using the same route. For example, differences in the configurations ofNAT devices or other network differences may mean one endpoint can bereached via a particular route even if the reverse route is notavailable.

Accordingly, the endpoint 1901 sends out three presence messages insteps 2112, 2114, and 2116. As the current example uses SIP messagingtransported via UDP, the message is a SIP INFO message. Morespecifically, in step 2112, the endpoint 1901 sends a SIP INFO messageto the private IP address/port pair of the endpoint 104 (i.e., via theprivate route). In step 2114, the endpoint 1901 sends a SIP INFO messageto the public (NAT) IP address/port pair of the endpoint 104 (i.e., viathe public route). In step 2116, the endpoint 1901 sends a SIP INFOmessage to the endpoint 104 via the reflector 1002 (i.e., via the relayroute), which is reflected to the endpoint 104 in step 2118.

The present example assumes that the endpoint 104 receives one or moreof the messages sent in steps 2112, 2114, and 2116. If more than onemessage is received, the endpoint 104 may respond only to the first onereceived. Accordingly, only one of steps 2120A, 2120B, and 2120C-1 mayoccur in the present example. Step 2120C-2 is dependent on theoccurrence of step 2120C-1 because the response message will not bereflected unless the relay route is used. The response message returnedby the endpoint 104 is a SIP 200 OK message that identifies which of theroutes was successful (e.g., was received first).

If the first (or only) SIP INFO message received by the endpoint 104from the endpoint 1901 is received via the same route as that used bythe endpoint 104 to send messages to the endpoint 1901 (e.g., theprivate route), then the communication session is established withmessages going both ways on that route. At this point, the table maythen be updated as shown in Table 3 below:

TABLE 3 Buddy Endpoint Route (send-receive) 1901 pr-pr X X X X

However, the first (or only) SIP INFO message received by the endpoint104 from the endpoint 1901 may be received on a different route thanthat used by the endpoint 104 to send messages to the endpoint 1901.When this occurs, the endpoint 104 flags this as the endpoint 1901responded to the INFO message via one route but is now communicating viaanother route. For example, the endpoint 1901 responded on the privateroute, but is now using the public route. One possibility for thisdiscrepancy is that there is a router or other network deviceinterfering with the return path (i.e., the path used by the endpoint1901 to send messages to the endpoint 104). Another possibility is thata message went faster one way than another way. For example, while theendpoint 1901 may have received the private message from the endpoint104 (i.e., the message of step 2102 of FIG. 21) before the othermessages, the endpoint 104 may have received the public message from theendpoint 1901 (i.e., the message of step 2114 of FIG. 21) before thepublic and relay messages.

When this occurs, the endpoint 104 may transition from the private routeto the public route. This results in sending and receiving routes ofpu-pu as illustrated by Table 4 below:

TABLE 4 Buddy Endpoint Route (send-receive) 1901 pu-pu X X X X

The endpoint 104 may also be configured to confirm that this transitionis correct. To confirm the transition, the endpoint 104 executes aconfirmation process and sends a confirmation message to the endpoint1901 on the private route (i.e., the route that the endpoint 104 thinksit should be using to send messages to the endpoint 1901). In thepresent example, the confirmation message may include a SIP field namedMAX_FORWARDS that defines a maximum number of hops that a packet cantake before being dropped. The MAX_FORWARDS field has a standard defaultvalue of seventy, but the endpoint 104 may set the value to one (i.e.,MAX_FORWARDS=1). If the response message from the endpoint 1901 isreceived by the endpoint 104 and has set the MAX_FORWARDS field to 0,then the endpoint 104 transitions back to the private route and usesthat route for sending future messages. This results in differentsending and receiving routes as illustrated by Table 5 below:

TABLE 5 Buddy Endpoint Route (send-receive) 1901 pr-pu X X X X

However, if the endpoint 104 does not receive a response message to itsconfirmation message, it continues using the public route. This resultsin sending and receiving routes of pu-pu as illustrated by Table 4above.

Communications between the endpoints 104 and 106 as illustrated in FIG.19B may follow the same sequence of presence messages and responses asthat described above with respect to FIGS. 20 and 21. However, since theendpoints 104 and 106 are in separate networks (i.e., not the same localnetwork), the private route 1902 is not available and the privatepresence messages will fail to reach their destination. The presencemessages may still be sent each way on the private route as theendpoints 104 and 106 do not know the location of the other endpoint,but the messages will be dropped. For example, the NAT devices 1004 and1006 may both be routers that have an address of 192.168.1.1 in theirrespective home networks. The NAT device 1004 may assign a privateaddress of 192.168.1.10 to the endpoint 104 and the NAT device 1006 mayassign a private address of 192.168.1.15 to the endpoint 106. Althoughthese addresses appear to be in the same local network, they are not.However, as the endpoints 104 and 106 have no way of knowing whether theprivate addresses are in the same local network until they perform theirstrategic routing sequences, they may both send their private presencemessages along the private route, even though the messages will bothfail. Accordingly, the endpoints 104 and 106 will use the public route1904 and/or the relay route 1906 when communicating.

Referring to FIG. 22, a flowchart illustrates one embodiment of a method2200 that may represent a process by which an endpoint such as theendpoint 104 of FIGS. 19A and 19B establishes a connection with anotherendpoint as described with respect to FIGS. 20 and 21 above.

In step 2202, the endpoint 104 sends outbound presence messages on theprivate, public, and relay routes. The presence messages may containidentifiers such as tags or other route indicators, or the receivingendpoint may simply note which virtual interface (i.e., pr, pu, or rl)received a particular presence message and correlate the message withthe route upon receipt. In step 2204, the endpoint 104 receives aresponse message that indicates which of the presence messages wasreceived first. For example, the response message may include the tagfrom the presence message to identify the route corresponding to thereceived presence message. In step 2206, the endpoint 104 selects theidentified route as the initial outbound route for messages being sentto the other endpoint.

In step 2208, the endpoint receives one or more inbound presencemessages from the other endpoint. In step 2210, the endpoint 104 sends aresponse to the first received inbound presence message.

In step 2212, the endpoint 104 determines whether the inbound route ofthe message received in step 2210 is the same route as the initialoutbound route selected in step 2206. If the routes are the same, themethod 2200 continues to step 2220 and uses the initial outbound routeto send messages to the other endpoint. If the routes are not the same,the method 2200 moves to step 2214 and sends a confirmation message tothe other endpoint using only the initial outbound route. In step 2216,the endpoint 104 determines whether a response to the confirmationmessage has been received. If no response to the confirmation messagehas been received, the method 2200 moves to step 2218 and transitions tothe inbound route as the new outbound route for messages being sent tothe other endpoint. If a response to the confirmation message has beenreceived, the method 2200 continues to step 2220 and uses the initialoutbound route to send messages to the other endpoint.

In step 2222, the endpoint 104 may begin sending keep-alive messages tothe other endpoint to ensure that the outbound route remains open. Forexample, one of the networks or NAT devices involved in the establishedsession may undergo a configuration change or a failure while the twoendpoints are online, and so an existing route may become unusable. Insuch a case, the endpoint may detect that the keep-alive messages arefailing and so may return to step 2202 to re-establish a valid route. Itis noted that the other endpoint may not need to re-establish itsoutbound route. For example, if the inbound and outbound routes for theendpoint 104 are different, the inbound route may remain valid eventhough the outbound route is invalid. Accordingly, some steps of themethod 2200 may be skipped in some scenarios.

It is noted that many different variations of the method 2200 may exist.For example, the endpoint 104 may transition to the inbound route as thenew outbound route if it is determined in step 2212 that the routes arenot the same, rather than remaining on the initial outbound route. Then,if a response is received to the confirmation message, the endpoint 104may transition back to the initial outbound virtual interface.Furthermore, as stated previously, the response message may never bereceived by the endpoint 104 and so some steps of the method 2200 maynot occur or may occur in a different order as there may be no responsemessage available to determine the initial outbound route. It is alsonoted that some steps of the method 2200 may be performed in a differentorder than shown. For example, step 2208 may occur before step 2204depending on network latency and other factors.

Referring to FIGS. 23A and 23B, in another embodiment, the endpoints 104and 106, the two NAT devices 1004 and 1006, and the stateless reflector1002 of FIGS. 19A and 19B are illustrated with a tunneling server orother access device 2302 and another endpoint 2304. The tunneling server2402 may provide access to other endpoints for an endpoint that does nothave UDP access or access to another expected protocol. For example, ifthe endpoint 104 performs a STUN request and the request fails, thenetwork within which the endpoint 104 is positioned may not support UDP(e.g., the network may be an Enterprise network that has disabled UDP).For purposes of illustration, the endpoints 104 and 2304 are in aprivate network and not separated by the NAT device 1004, and theendpoint 106 is separated from the endpoint 104 by the NAT devices 1004and 1006.

Referring to FIG. 24, a sequence diagram illustrates one embodiment of amessage sequence 2400 that may occur in the environment of FIGS. 23A and23B to establish a connection between the endpoints 104 and 106. As withthe previous discussion of FIG. 20, the endpoints 104 and 106 may eachmaintain a table, although this is not shown in the present example.

In step 2402, the endpoint 104 sends a STUN request that fails. Based onthe failure of the STUN request, the endpoint 104 determines that thenetwork (e.g., the NAT device 1004) has disabled UDP. It is understoodthat other indicators may be used to determine that UDP is notavailable. In step 2404, based on the unavailability of UDP, theendpoint 104 opens a TCP/IP connection (i.e., a tunnel) with thetunneling server 2302. This connection may use a port such as port 443of the NAT device 1004, which is the default TCP port for HTTP Secure(HTTPS) connections using the Transport Layer Security (TLS) or SecureSocket Layer (SSL) protocols. However, it is understood that port 443 isonly an example and that other available ports may be used. In step2406, the endpoint 104 requests a shadow IP address and shadow port onthe tunneling server 2302. In step 2408, the tunneling server 2302creates the shadow IP address and port and returns this information tothe endpoint 104 in step 2410.

The shadow IP address and shadow port serve as the public address andport of the endpoint 104 for other endpoints. In other words, the shadowIP address/port replace the NAT IP address/port that would serve as thepublic contact information for the endpoint 104 in an environment inwhich UDP is available to the endpoint 104 (e.g., as in FIGS. 19A and19B). In some embodiments, the shadow IP address/port pairs may beplaced on a shadow list as they are provisioned and the shadow list maybe available to the access server 102 and/or endpoints. In otherembodiments, the access server 102 and/or endpoints may have a list orrange of IP addresses/ports that are known to be shadows. In still otherembodiments, the knowledge of whether an IP address/port is a shadow isnot available to the access server 102 and/or endpoints.

In step 2412, the endpoint 104 authenticates with the access server 102via the tunnel using its local IP address/port and shadow address/portinformation. In step 2414, the access server 102 authenticates theendpoint 104 and sends the endpoint 104 the contact information ofonline buddies, including corresponding private, public, and shadow IPaddress/port information.

Although not shown in FIG. 24, the endpoint 106 sends a request to aSTUN server and receives its public IP address/port information asdescribed with respect to the endpoints 104 and 1901 in FIG. 20. Sincethe endpoint 106 is successful with its STUN request, it does not needto use the tunneling server 2302. In steps 2416 and 2418, the endpoint106 authenticates with the access server and receives the private IPaddress/port and shadow IP address/port of the endpoint 104. Asdiscussed above, the endpoint 106 may or may not know that the endpoint104 is using a shadow, depending on the particular implementation of theshadow list.

In steps 2420 and 2422, the endpoints 104 and 106 may establish acommunication session as described previously with respect to FIGS. 20and 21. However, the communications between the two endpoints 104 and106 will use the tunnel between the endpoint 104 and the tunnelingserver 2302 and the corresponding shadow IP address and port for theendpoint 104.

In embodiments where the endpoint 106 knows that the endpoint 104 isusing a shadow, the endpoint 106 may not send a presence message via theprivate route as the endpoint 106 knows that the private route is notavailable. In other embodiments, the endpoint 106 may send a presencemessage via the private route even though the route is not available.

Communications between the endpoints 104 and 2304 as illustrated in FIG.23B may follow a similar sequence of presence messages and responses asthat described above with respect to FIG. 24. However, since theendpoints 104 and 2304 are in the same local network, the private route1902 is available and the private presence messages may reach theirdestinations. The endpoint 2304 may not use a relay message to try toreach the endpoint 104, since its failed STUN request will inform theendpoint 2304 that UDP is not available. In order to use the public andrelay routes, the endpoint 2304 will create a tunnel with the tunnelingserver 2303 as described above with respect to the endpoint 104. Thepublic and relay messages may still work via the respective tunnels ofthe endpoints 104 and 2304.

Referring to FIG. 25, in another embodiment, an environment 2500 isillustrated in which an endpoint 104 a (e.g., the endpoint 104 ofFIG. 1) is in a call with another endpoint 106. For purposes ofillustration, the term “call” as used in the following disclosure mayinclude the transmission and reception of audio, video, and/or data.While this call is ongoing, another endpoint 104 b logs in to thepeer-to-peer network using the same authentication information (i.e.,credentials) as the endpoint 104 a. In other words, from the perspectiveof the access server 102 (FIG. 1), the endpoints 104 a and 104 b aresimultaneous logins using the same login information (e.g., user nameand password). In the present embodiment, the call with the endpoint 106may be “swept” from the current endpoint 104 a to the newly logged inendpoint 104 b. This may occur, for example, if a user wants to move thecall from a desktop computer or laptop to another device such as a cellphone or vice versa. This may also occur if the endpoint 104 a istransitioning from one network type to another (e.g., WiFi to 3G).Rather than require the endpoints 104 a, 104 b, and 106 to go through aprocess where connections are broken and re-established, the act ofsweeping transitions the call by transferring information correspondingto the call from the endpoint 104 a to the endpoint 104 b.

In the present example, the endpoints 104 a, 104 b, and 106 each includestate machines that handle each call in which an endpoint may beinvolved. For example, the endpoint 104 a is involved in the call withthe endpoint 106 and a state machine within each of the endpoints 104 aand 106 handles this particular call for the respective endpoints. Thestate machines handling this call between the endpoints 104 a and 106may be synchronized in order to maintain the call. For example, thefollowing embodiments may be based on a SIP messaging model over UDP.SIP generally requires that the two endpoints be synchronized and thestate machines may be used to ensure this synchronization. An endpointmay have multiple ongoing calls and so may have multiple state machinescorresponding to those calls.

For purposes of example, a call is associated with a session. In thepresent embodiment, the term “session” refers to a call or a relatedseries of calls, such as a conference call. So, for example, a singleaudio call between the endpoints 104 a and 106 is a single session and aconference call between the endpoint 104 a and multiple other endpointsusing audio, video, and data is also a single session. If the endpoint104 a is engaged in multiple unrelated calls, then there are acorresponding number of sessions. So two separate audio calls with twoendpoints (e.g., as in call holding) would be two sessions. It isunderstood that different call and session relationships may exist andthat the present disclosure covers all such embodiments.

Each session is associated with information about that session. Thesession may include information such as IP addresses and ports needed tocommunicate with other endpoints, codecs used in the calls, and similarinformation. The session may also include information identifying thesession as a one-to-one call session or a one-to-many call session. Ifone-to-many, then the session may include information on each callinvolved in the session. For example, if the session is a conferencecall between the endpoint 104 a and two other endpoints, the session onthe endpoint 104 a would include two calls. Each call would be theconference call leg between the endpoint 104 a and one of the other twoendpoints. Each call in a session is associated with attributes aboutthat call. For example, the call is associated with informationindicating whether the call is audio only, audio and video, video only,data, application sharing, and/or other call types. Accordingly, asession is associated with the information needed to conduct thatsession by the corresponding endpoint.

In the present example, which uses a SIP based model, each call has aone-to-one correspondence with a SIP dialog. SIP generally uses anINVITE to request a call and a 200 OK to accept the call. The call setupprocess creates a SIP dialog that allows either side to hang up thecall. Unlike a text message that is one way, both sides need to be ableto act on a call and the SIP dialog enables this control to occur. TheSIP dialog contains the information needed for the call, such as the IPaddress and port information of the destination endpoint 106, the typeof call (e.g., audio, video, or audio/video), codecs used, the state ofthe corresponding state machines (e.g., an INVITE has been sent and thestate machine is waiting for the 200 OK response), and other neededinformation. Detailed information about SIP can be found in RFC 3261 bythe Internet Engineering Task Force (IETF) Network Working Group, whichis hereby incorporated by reference in its entirety.

Referring to FIG. 26, a sequence diagram illustrates one embodiment of amessage sequence 2600 that may occur in the environment 2500 of FIG. 25when a session is swept from the endpoint 104 a to the endpoint 104 b.In the present example, the endpoint 104 a/104 b is a buddy to theendpoint 106 and so each has already authorized communications from theother buddy as described in previous embodiments. Furthermore, as shownby step 2602, the endpoints 104 a and 106 have already logged into thepeer-to-peer network and are online and engaged in a call prior to theinitial action by the endpoint 104 a. Although the call is an audio callin the present example, it is understood that it can be any type of callthat can be handled by the endpoints 104 a and 106.

In step 2604, the endpoint 104 b logs in to the peer-to-peer network viathe access server 102 as described previously. For example, the endpoint104 b may send a STUN request to obtain its public IP address and portinformation, and then send this information to the access server 102with a username, password, and private (NAT) IP address and portinformation. In step 2606, after authenticating the endpoint 104 b, theaccess server 102 responds with the buddy list corresponding to thelogin information. This process is described above and not repeated indetail in the present example. The buddy list may contain an entryindicating that the endpoint 104 a is also logged in or an additionalindicator or other message may be used to inform the endpoint 104 b ofthe online presence of the endpoint 104 a. This informs the endpoint 104b that there is a pre-existing simultaneous login from a differentendpoint.

In step 2608, the endpoint 104 b sends presence messages to the endpoint106 and to other endpoints (not shown) that are shown as online by thebuddy list received in step 2606. The presence messages inform the otherendpoints that the endpoint 104 b is online. Although not specificallyillustrated in FIG. 26, in the present example the messages are SIPpresence messages. In step 2610, the each endpoint may respond with a200 OK in acknowledgement, including the endpoint 106. As theseresponses may be received over a period of time, step 2610 is shown asoccurring through a number of later steps. However, it is understoodthat the responses may be received immediately following step 2608 andprior to step 2612, may all occur after step 2616, or may be dispersed.Accordingly, the exact time that a presence message is received is notillustrated in FIG. 26. The endpoint 104 b does not send a presencemessage to the endpoint 104 a in the present example, but such a messagemay be sent in some embodiments. Although SIP is used for purposes ofexample, it is understood that many different types of messaging may beused and the presence message and reply may not be SIP messages.

In step 2612, the endpoint 104 b sends a “go away” message to theendpoint 104 a. Upon receipt of this message, the endpoint 104 a checksfor a policy related to such a message and determines how the endpoint104 a is to respond. In the present example, because the endpoint 104 ais currently in a call with the endpoint 106, the policy indicates thatthe call is to be swept to the endpoint 104 b. Accordingly, in step2616, the endpoint 104 a begins sending session informationcorresponding to the audio call to the endpoint 104 b. As the currentembodiment uses a SIP dialog model, this information is the SIP dialog,such as state information, codec types, and information about theendpoint on the other end of the call (i.e., the endpoint 106). Theendpoint 104 a may send the SIP dialog based on a timer that provides adefined window of time. Once the timer expires, the endpoint 104 a mayclose even if the SIP dialog has not been completely transferred to theendpoint 104 b.

The endpoint 104 b begins receiving and buffering the sessioninformation and may also be receiving responses to the presence messagesit sent in step 2608. Once the SIP dialog is received, the endpoint 104b checks the incoming response messages for an endpoint corresponding tothe destination identified in the SIP dialog (or destinations, if morethan one endpoint is involved). If the response message from theendpoint 106 was received prior to the receipt of the SIP dialog, thenthe endpoint 104 b will identify the endpoint 106 as the destination inthe SIP dialog. If the response message from the endpoint 106 has notbeen received prior to the receipt of the SIP dialog, then the endpoint104 b may compare each response message to the buffered SIP dialog asthey are received until the endpoint 106 is identified as thedestination in the SIP dialog.

If no match is found, the endpoint 104 b may simply ignore the SIPdialog. In this case, the endpoint 104 b may operate as a “new” endpointwith no existing calls. To re-establish the call with the endpoint 106,either the endpoint 104 b or the endpoint 106 would need to set up a newcall.

In step 2618, after receiving the SIP dialog and identifying theendpoint 106, the endpoint 104 b performs a STUN request (not shown) andsends an update message to the endpoint 106. In the present embodiment,the update message is the SIP out-of-band signaling message UPDATE. TheUPDATE message may include a Session Description Protocol (SDP)description into which information needed to transition the call isinserted, including the STUN information just obtained. In step 2620,the endpoint 106 performs a STUN request (not shown) and responds to theUPDATE with a 202 OK that includes an SDP with the information needed bythe endpoint 104 b, including the STUN information just obtained.

During this process, the endpoint 106 may have continued sending packetsto the endpoint 104 a. Accordingly, after receiving the update, theendpoint 106 may stop sending the packets in step 2622. Although shownas occurring after step 2620, it is understood that step 2622 may occurbetween steps 2618 and 2620. In step 2624, the endpoint 104 b and theendpoint 106 continue the call previously existing between the endpoint104 a and 106.

Referring to FIG. 27, a flow chart illustrates one embodiment of amethod 2700 that may be used by the endpoint 104 b in the environment ofFIG. 25. In the present example, the endpoint 104 a/104 b is a buddy tothe endpoint 106 and so each has already authorized communications fromthe other buddy as described in previous embodiments. Furthermore, theendpoints 104 a and 106 have already logged into the peer-to-peernetwork and are online and engaged in a call prior to the initial stepof the method 2700. Although the call is an audio call in the presentexample, it is understood that it can be any type of call that can behandled by the endpoints 104 a and 106.

In step 2702, the endpoint 104 b logs in to the peer-to-peer network viathe access server 102. For example, as described with respect to FIGS. 4and 5, the endpoint 104 b may send a STUN request to obtain its publicIP address and port information, and then send this information to theaccess server with a username, password, and private (NAT) IP addressand port information. In response to the login request and theauthentication information, the access server 102 returns the buddy listto the endpoint 104 b. The buddy list includes such information as whichbuddies are online and routing information needed to contact each of theonline buddies. The buddy list indicates that the endpoint 106 isonline. The access server 102 may also include the endpoint 104 a on thebuddy list due to detecting the simultaneous login by the endpoint 104b. In other embodiments, the access server 102 may notify the endpoint104 b of the online presence of the endpoint 104 a in other ways, suchas by another indicator in the buddy list or via a separate message.

In step 2704, the endpoint 104 b sends presence messages to the onlinebuddies to inform them that the endpoint 104 b is now online andavailable. In the present embodiment, the endpoint 104 b expects toreceive a response message from each of the buddy endpoints, but it isunderstood that such responses may not be expected in some embodiments.In some embodiments, the endpoint 104 b may not send a presence messageto the endpoint 104 a, but may instead send the “go away” message ofstep 2708. In such embodiments, the endpoint 104 b may perform step 2706prior to step 2704 to determine whether there is a simultaneous login.

In step 2706, the endpoint 104 b determines whether there is an endpointthat is logged in to the peer-to-peer network using the sameauthentication information as the endpoint 104 b. In other words, theendpoint 104 b determines whether there is a simultaneous login withanother endpoint. If there is no simultaneous login, the method 2700moves to step 2724, where it operates as a newly logged in endpoint. Ifthere is a simultaneous login, the method 2700 moves to step 2708, wherethe endpoint sends a “go away” message to the endpoint 104 a. Theactions of the endpoint 104 a in response to this message will bedescribed below with respect to FIG. 28.

In step 2710, the endpoint 104 b receives responses to its presencemessages sent in step 2704 and session information from the endpoint 104a in response to the “go away” message sent in step 2708. It is notedthat, in the present example, there is session information to bereceived from the endpoint 104 a because the endpoint 104 a is currentlyin a session with the endpoint 106. However, if the endpoint 104 a wasnot in a session, the endpoint 104 b would not receive any sessioninformation and steps 2714 through 2722 would be skipped.

Accordingly, in step 2712, a determination is made as to whether anysession information has been or is being received from the endpoint 104a. If no session information is received, the method 2700 moves to step2724. The lack of session information may occur for various reasons,such as a failure on the part of the endpoint 104 a or simply becausethe endpoint 104 a is not currently engaged in a session. In the presentembodiment, the endpoint 104 b is not concerned with why there is nosession information and proceeds normally. While the present exampleillustrates the endpoint 104 a as simply starting sending the sessioninformation upon receipt of the “go away” message, it is understood thatvarious messages may be exchanged between the endpoints 104 a and 104 bindicating that there is session information available for transfer.

If session information is received, the method 2700 moves to step 2714,where a determination is made as to whether the other endpoint (i.e.,the endpoint 106) involved in the session matches one of the endpointsthat responded to a presence message. In the present example, thesession information is in the form of one or more SIP dialogs asdescribed with respect to FIG. 26. Accordingly, the endpoint 104 b mustreceive the entire dialog before it can identify the other endpointinvolved in the session. Other embodiments may allow for identificationof the endpoint 106 prior to the receipt of all the session information.

It is understood that, from the time the first presence message is sentout until the last response is received (if all responses are received),the endpoint 104 b may be receiving responses to the presence messages.Therefore, the response from the endpoint 106 may come at any timerelative to the transfer of the session information represented by theSIP dialog. The response from the endpoint 106 may be received by theendpoint 104 prior to the receipt of the entire SIP dialog orafterwards. As such, steps 2710 and 2714 may overlap. For example, theendpoint 104 b may receive and buffer the entire SIP dialog and compareany received responses to the endpoint 106 identified in the dialog. Ifthe response from the endpoint 106 has already been received, theendpoint 104 b may then match the response to the dialog and move tostep 2716. However, if the response from the endpoint 106 has not yetbeen received, then the endpoint 104 b may wait for additional presencemessages until a match is found or until some other event occurs. Forexample, the waiting period may time out or otherwise end to prevent theendpoint 104 b from waiting indefinitely. If this occurs and no match isfound, the method 2700 moves to step 2724.

If a match is found in step 2714, the method 2700 moves to step 2716 andperforms a STUN request, sets up ports for the session, and performs anyother needed activity in preparation for continuing the session receivedfrom the endpoint 104 a. Step 2716 may also include performing any NATtraversal or strategic routing messaging and/or determinations asdescribed in previous embodiments. In step 2718, the endpoint 104 bsends a message to the endpoint 106 to inform the endpoint 106 that theendpoint 104 b is taking over the session. For example, the message maybe an UPDATE message containing SDP information with the STUNinformation obtained in step 2716 and other information that may beneeded to communicate with the endpoint 104 b.

In step 2720, the endpoint 104 b receives a response to the UPDATE(assuming a response was sent successfully by the endpoint 106). Theendpoint 104 b extracts any needed information from the UPDATE response(e.g., from SDP information containing IP and port information for theendpoint 106). In step 2722, the endpoint 104 b continues the sessionwith the endpoint 106. While the session is ongoing, the endpoint 104 bmay also operate as a normal endpoint and perform any endpoint functionsdescribed herein. It is understood that this process of sweeping thesession onto the endpoint 104 b may occur without user intervention orknowledge, although the user may set the policy for the endpoint 104a/104 b that defines what is to be swept.

In some embodiments, rather than receiving the session information viapacket transfer over a wireline or wireless connection, the sessioninformation may be retrieved from memory. More specifically, theendpoints 104 a and 104 b may exist on the same client or may otherwisehave access to shared memory that is available to both endpoints. Insuch embodiments, the session information may be stored in memory by theendpoint 104 a and retrieved from the same memory by the endpoint 104 b.This memory transfer may occur when the client is moving from onenetwork type to another network type (e.g., WiFi to 3G) and in any othercase where such a memory transfer is possible if such a transfer isdesired. In such cases, an internal transition within the client mayoccur from the endpoint 104 a to the endpoint 104 b to account for thenetwork change or other scenario. The retrieval of the sessioninformation from memory would occur in step 2710, with the other stepsremaining the same. Accordingly, even if on the same physical client asthe endpoint 104 a, the endpoint 104 b may login, send presencemessages, and perform the other functions described with respect to themethod 2700. It is noted that the memory transfer embodiments mayinclude embodiments in which some information (e.g., memory locationsand/or the “go away” message) is exchanged between the endpoint 104 aand the endpoint 104 b via a wireline or wireless connection.

Referring to FIG. 28, a flow chart illustrates one embodiment of amethod 2800 that may be used by the endpoint 104 a in the environment ofFIG. 25. In the present example, the endpoint 104 a/104 b is a buddy tothe endpoint 106 and so each has already authorized communications fromthe other buddy as described in previous embodiments. Furthermore, theendpoints 104 a and 106 have already logged into the peer-to-peernetwork and are online and engaged in a call prior to the initial stepof the method 2800. Although the call is an audio call in the presentexample, it is understood that it can be any type of call that can behandled by the endpoints 104 a and 106.

In step 2802, while the session with the endpoint 106 is ongoing, theendpoint 104 a receives a “go away” message from the endpoint 104 b. Instep 2804, the endpoint 104 a checks for any applicable policies and, inthe present example, identifies a policy that is to be applied if a “goaway” message is received. Although not shown, it is understood thatthere may be no applicable policy, in which case the method 2800 mayend. However, as there is an applicable policy in the present example,the method moves to step 2806.

In step 2806, the endpoint 104 a determines whether there is an activesession. If there is not an active session, the method 2800 moves tostep 2816 and follows the next policy action (if any). This may be toshut down, to send out offline messages and go to slave status, or toperform any other action defined in the policy.

As the determination of step 2806 identifies that there is an activesession with the endpoint 106, the method moves to step 2808. In step2808, the endpoint 104 a may determine whether the session is to beswept to the endpoint 104 b. This may be defined in the policy. Forexample, the policy may define that all sessions are to be swept, thatonly certain types of sessions (e.g., voice only) or sessions withcertain endpoints are to be swept, and/or that only certain types ofsessions are not to be swept (e.g., file transfers). It is understoodthat these are only examples and that many different criteria may beused in the policy to define whether a session is to be swept. Althoughnot shown, in some embodiments, the user of the endpoints 104 a/104 bmay receive a prompt or other indicator to confirm that the session isto be swept. If the determination of step 2808 indicates that thesession is not to be swept, the endpoint 104 a moves to step 2816. Ifthe determination indicates that the session is to be swept, the method2800 continues to step 2810.

In step 2810, the endpoint 104 a sends the session information to theendpoint 104 b. This information may be SIP dialog information aspreviously described or may be other information needed by the endpoint104 b to maintain the session with the endpoint 106. For example, thesession information may include IP address and port information, calltype (e.g., audio only or audio and video), any codecs used in the call,state information, and/or any other needed information.

In step 2812, the endpoint 104 a may determine whether a timer hasexpired. In the present example, the endpoint 104 a may wait for one ormore responses from the endpoint 104 b regarding the sessioninformation. In order to prevent the endpoint 104 a from waitingindefinitely if a response is not received, a timer may be used toprovide a defined window of time in which the session information is tobe sent. The window may be static (e.g., a defined period of time fromthe first packet sent to the endpoint 104 b or based on another marker)or may be dynamic (e.g., based on the amount of information to send orresetting each time a response is received). If the time has expired asdetermined in step 2812, the method 2800 moves to step 2816. If thetimer is not expired, the method 2800 moves to step 2814.

In step 2814, the endpoint 104 a may determine whether the sessioninformation has all been sent. If not, the method 2800 returns to step2810. If all the session information has been sent, the method 2800moves to step 2816.

As described with respect to FIG. 27, in some embodiments, the sessioninformation may be transferred via memory rather than via packettransfer over a wireline or wireless connection. In such embodiments,the session information may be stored in memory by the endpoint 104 a instep 2810 rather than sent to the endpoint 104 b. Steps 2812 and 2814may be omitted or may be replaced with suitable memory controlinstructions to ensure that the session information is properly stored.Accordingly, the endpoint 104 a may notify the endpoint 104 b of thestorage location(s) rather than actually send the session information tothe endpoint 104 b. Even if on the same physical client as the endpoint104 b, the endpoint 104 a may check the policy, determine whether thereis an active session, determine whether the session is to be swept, andperform some or all of the other functions described with respect to themethod 2800.

Referring to FIG. 29, a flow chart illustrates one embodiment of amethod 2900 that may be used by the endpoint 106 in the environment ofFIG. 25. In the present example, the endpoint 104 a/104 b is a buddy tothe endpoint 106 and so each has already authorized communications fromthe other buddy as described in previous embodiments. Furthermore, theendpoints 104 a and 106 have already logged into the peer-to-peernetwork and are online and engaged in a call prior to the initial stepof the method 2900. Although the call is an audio call in the presentexample, it is understood that it can be any type of call that can behandled by the endpoints 104 a and 106.

In step 2902, the endpoint 106 receives an update message from theendpoint 104 b. The update message may be a SIP UPDATE as describedabove or may be any other type of message. The endpoint 106 extractsinformation from the update message and begins to transition the sessionto the endpoint 104 b. In the present embodiment, it is noted that theUPDATE message basically operates as a request from the endpoint 104 bthat the endpoint 106 automatically accepts (e.g., without any actionneeded by the user of the endpoint 106). In other words, the endpoint104 b may be viewed as placing a call to the endpoint 106 that isautomatically accepted, rather than requiring the user of the endpoint106 to answer the call.

In step 2904, the endpoint 106 performs a STUN request and any otheractions needed to establish the session with the endpoint 104 b. Forexample, the endpoint 106 may set up any needed new port(s) and/or mayupdate the information corresponding to the current session to point tothe endpoint 104 b rather than the endpoint 104 a. Step 2904 may alsoinclude performing any NAT traversal or strategic routing messagingand/or determinations as described in previous embodiments. In step2906, the endpoint 106 sends any needed information to the endpoint 104b, such as the results of the STUN request.

During this time, the endpoint 106 may have continued sending packets tothe endpoint 104 a. Accordingly, in step 2908, the endpoint 106 stopssending packets associated with the session to the endpoint 104 a andonly sends those packets to the endpoint 104 b. The endpoint 106 mayterminate the connection or may update the internal audio connection toroute everything to the endpoint 104 b. In step 2910, the endpoint 106continues the session with the endpoint 104 b.

It is understood that sweeping may be not be used for some types ofsessions. For example, a file transfer session may not be swept. If theendpoint 104 a is transferring a file to the endpoint 106, sweeping thesession would be pointless if the file was not also on the endpoint 104b. If the endpoint 106 is sending the file to the endpoint 104 a,sweeping the session would be pointless since the entire file might aswell be resent by the endpoint 106 to the endpoint 104 b. In embodimentswhere the endpoints 104 a and 104 b are on the same physical device,sweeping a file transfer session may be appropriate as the two endpointsmay have access to the same memory where the file is being bufferedduring the transfer. Other types of file transfer may be swept if, forexample, a document or other file is being displayed by the endpoint106. Sweeping the session may then entail transferring the currentlyviewed page or other portion of a file to the endpoint 104 b, ratherthan the entire file. Instructions regarding sweeping may be defined inthe policy stored in the endpoints 104 a and/or 104 b.

Accordingly, described above are embodiments illustrating how anendpoint in a peer-to-peer network can sweep an ongoing session toanother endpoint. Although the embodiments herein describe the sweepingas occurring between endpoints that are simultaneously logged in, it ispossible to sweep a session between two different endpoints that arelogged in using different authentication credentials. It is understoodthat additional authorization may be required (e.g., an endpoint mayneed authorization to allow such sweeping to occur to and/or fromanother endpoint), but such sweeping may occur in a similar manner tothe embodiments described above with respect to messaging, sessioninformation transfer, and similar actions.

Referring to FIG. 30, one embodiment of a computer system 3000 isillustrated. The computer system 3000 is one possible example of asystem component or device such as an endpoint or an access server. Thecomputer system 3000 may include a central processing unit (“CPU”) 3002,a memory unit 3004, an input/output (“I/O”) device 3006, and a networkinterface 3008. The components 3002, 3004, 3006, and 3008 areinterconnected by a transport system (e.g., a bus) 3010. A power supply(PS) 3012 may provide power to components of the computer system 3000,such as the CPU 3002 and memory unit 3004. It is understood that thecomputer system 3000 may be differently configured and that each of thelisted components may actually represent several different components.For example, the CPU 3002 may actually represent a multi-processor or adistributed processing system; the memory unit 3004 may includedifferent levels of cache memory, main memory, hard disks, and remotestorage locations; the I/O device 3006 may include monitors, keyboards,and the like; and the network interface 3008 may include one or morenetwork cards providing one or more wired and/or wireless connections tothe packet network 108 (FIG. 1). Therefore, a wide range of flexibilityis anticipated in the configuration of the computer system 3000.

The computer system 3000 may use any operating system (or multipleoperating systems), including various versions of operating systemsprovided by Microsoft (such as WINDOWS), Apple (such as Mac OS X), UNIX,and LINUX, and may include operating systems specifically developed forhandheld devices, personal computers, and servers depending on the useof the computer system 3000. The operating system, as well as otherinstructions (e.g., for the endpoint engine 252 of FIG. 2 if anendpoint), may be stored in the memory unit 3004 and executed by theprocessor 3002. For example, if the computer system 3000 is the endpoint104 b, the memory unit 3004 may include instructions for sending andreceiving messages, receiving the session information from the endpoint104 a, and continuing the session with the endpoint 106.

In another embodiment, a method comprises receiving, by a firstendpoint, an update message directly from a second endpoint, wherein theupdate information instructs the first endpoint to transitioncommunications corresponding to an active session occurring between thefirst endpoint and a third endpoint from the third endpoint to thesecond endpoint and wherein the update message includes informationcorresponding to the second endpoint that is needed by the firstendpoint in order to communicate with the second endpoint; sending, bythe first endpoint, a response to the update message directly to thesecond endpoint, wherein the response includes information correspondingto the first endpoint that is needed by the second endpoint in order tocommunicate with the first endpoint; and transitioning, by the firstendpoint, communications corresponding to the active session from thethird endpoint to the second endpoint, wherein packets sent by the firstendpoint are now sent directly to the second endpoint instead of thethird endpoint. The transitioning may include updating, by the firstendpoint, routing information associated with the active session on thefirst endpoint, wherein the update changes the routing information fromidentifying the third endpoint as the destination to identifying thesecond endpoint as the destination. The transitioning may includeestablishing a new call leg with the second endpoint for the activesession and terminating an existing call leg for the active session withthe third endpoint.

In yet another embodiment, a method for sweeping an active sessionexisting between a first endpoint and a second endpoint from the firstendpoint to a third endpoint comprises providing, by the third endpoint,authentication credentials to an access server to gain access to apeer-to-peer network, wherein the access server returns a buddy listassociated with the authentication credentials to the third endpoint inresponse, and wherein the second endpoint is included on the buddy listas an endpoint with which the third endpoint is authorized tocommunicate; identifying, by the third endpoint, that the first andthird endpoints are simultaneously logged in because they gained accessto the peer-to-peer network using identical authentication credentials;sending, by the third endpoint, a go away message directly to the firstendpoint; receiving, by the third endpoint, session information from thefirst endpoint corresponding to the active session occurring between thefirst and second endpoints, wherein the session information includesinformation needed by the third endpoint to participate in the activesession with the second endpoint; sending, by the third endpoint, anupdate message directly to the second endpoint, wherein the updatemessage instructs the second endpoint to transition the active sessionfrom the first endpoint to the second endpoint and includes informationneeded for the second endpoint to transition the active session from thefirst endpoint to the third endpoint; and receiving, by the thirdendpoint, a response to the update message from the second endpoint,wherein the response includes information needed for the third endpointto participate in the active session with the second endpoint. Themethod may further comprise sending, by the third endpoint, a presencemessage directly to the second endpoint to notify the second endpointthat the third endpoint is online. The method may further comprisereceiving, by the third endpoint, a response to the presence messagedirectly from the second endpoint, wherein the response identifies thesecond endpoint as the sender of the response; and determining, by thethird endpoint, whether the second endpoint identified in the responseis the same as an endpoint identified in the session informationreceived from the first endpoint. Receiving the session information mayinclude receiving the session information by the third endpoint directlyfrom the first endpoint via one of a wireline and a wireless interface.Receiving the session information may include retrieving the sessioninformation by the third endpoint from a memory location accessible toboth the first endpoint and the third endpoint. The session informationmay include Session Initiation Protocol (SIP) dialog information. Theupdate message may be a SIP UPDATE message. The session information mayinclude state information needed to synchronize a state machine on thethird endpoint with a state machine on the second endpoint. The firstand third endpoints may be located on a single physical device.

In still another embodiment, a method for sweeping an active sessionexisting between a first endpoint and a second endpoint from the firstendpoint to a third endpoint comprises receiving, by the first endpoint,a go away message directly from the third endpoint; checking, by thefirst endpoint, a policy associated with the first endpoint to determinean action to be taken upon receipt of the go away message; identifying,by the first endpoint, that the first endpoint is engaged in an activesession with the second endpoint; and transferring, by the firstendpoint, session information to the third endpoint, wherein the sessioninformation includes information needed by the third endpoint to enterthe active session with the second endpoint. The method may furthercomprise determining, by the first endpoint, whether to transfer thesession information to the third endpoint based on the policy. Themethod may further comprise determining, by the first endpoint, whethera timer has expired, wherein the transferring occurs only within aperiod of time defined by the timer. The transferring the sessioninformation may include sending the session information directly fromthe first endpoint to the third endpoint via one of a wireline and awireless interface. The transferring the session information may includestoring the session information by the first endpoint in a memorylocation accessible to both the first endpoint and the third endpoint.The session information may include Session Initiation Protocol (SIP)dialog information. The session information may include stateinformation needed to synchronize a state machine on the third endpointwith a state machine on the second endpoint. The first and thirdendpoints may be located on a single physical device.

In another embodiment, a system comprises a network interface; aprocessor coupled to the network interface; and a memory coupled to theprocessor and containing a plurality of instructions for execution bythe processor, the instructions including instructions for configuring athird endpoint stored at least partially in the memory to sweep anactive session existing between a first endpoint and a second endpointfrom the first endpoint to the third endpoint by providing, by the thirdendpoint, authentication credentials to an access server to gain accessto a peer-to-peer network, wherein the access server returns a buddylist associated with the authentication credentials to the thirdendpoint, and wherein the second endpoint is included on the buddy listas an endpoint with which the third endpoint is authorized tocommunicate; identifying, by the third endpoint, that the first andthird endpoints are simultaneously logged in because they gained accessto the peer-to-peer network using identical authentication credentials;sending, by the third endpoint, a go away message directly to the firstendpoint; receiving, by the third endpoint, session information from thefirst endpoint corresponding to the session occurring between the firstand second endpoints, wherein the session information includesinformation needed by the third endpoint to participate in the sessionwith the second endpoint; sending, by the third endpoint, an updatemessage directly to the second endpoint, wherein the update messageinstructs the second endpoint to switch the active session from thefirst endpoint to the second endpoint and includes information neededfor the second endpoint to transition the active session from the firstendpoint to the third endpoint; and receiving, by the third endpoint, aresponse to the update message from the second endpoint, wherein theresponse includes information needed for the third endpoint toparticipate in the active session with the second endpoint. The systemmay further comprise instructions for the first endpoint, wherein thefirst endpoint is stored at least partially in the memory, theinstructions including: receiving, by the first endpoint, the go awaymessage directly from the third endpoint; checking, by the firstendpoint, a policy associated with the first endpoint to determine anaction to be taken upon receipt of the go away message; identifying, bythe first endpoint, that the first endpoint is engaged in the activesession with the second endpoint; and transferring, by the firstendpoint, session information to the third endpoint, wherein the sessioninformation includes information needed by the third endpoint to enterthe active session with the second endpoint. The transferring thesession information by the first endpoint may include storing thesession information by the first endpoint in a memory locationaccessible to both the first endpoint and the third endpoint, andwherein the receiving, by the third endpoint, the session informationincludes retrieving the session information by the third endpoint fromthe memory location. The system may include a power supply coupled tothe network interface, the processor, and the memory.

While the preceding description shows and describes one or moreembodiments, it will be understood by those skilled in the art thatvarious changes in form and detail may be made therein without departingfrom the spirit and scope of the present disclosure. For example,various steps illustrated within a particular sequence diagram or flowchart may be combined or further divided. In addition, steps describedin one diagram or flow chart may be incorporated into another diagram orflow chart. Some steps may be performed in an order different from thatshown and/or may overlap. Furthermore, the described functionality maybe provided by hardware and/or software, and may be distributed orcombined into a single platform. Additionally, functionality describedin a particular example may be achieved in a manner different than thatillustrated, but is still encompassed within the present disclosure.Therefore, the claims should be interpreted in a broad manner,consistent with the present disclosure.

What is claimed is:
 1. A method for sweeping an active session existingbetween a first endpoint and a second endpoint from the first endpointto a third endpoint, the method comprising: providing, by the thirdendpoint, authentication credentials to an access server to gain accessto a peer-to-peer network, wherein the access server returns a profilecontaining a buddy list associated with the authentication credentialsto the third endpoint in response, and wherein the second endpoint isincluded on the buddy list as an endpoint with which the third endpointis authorized to communicate; identifying, by the third endpoint, basedon the profile that the first and third endpoints are simultaneouslylogged in because they gained access to the peer-to-peer network usingidentical authentication credentials; sending, by the third endpoint, apeer-to-peer go away message directly to the first endpoint; receiving,by the third endpoint, session information from the first endpointcorresponding to the active session occurring between the first andsecond endpoints, wherein the session information includes informationneeded by the third endpoint to participate in the active session withthe second endpoint, and wherein the session information is received viapeer-to-peer messaging between the first endpoint and the thirdendpoint; sending, by the third endpoint, a peer-to-peer update messagedirectly to the second endpoint, wherein the update message instructsthe second endpoint to transition the active session from the firstendpoint to the third endpoint and includes information needed for thesecond endpoint to transition the active session from the first endpointto the third endpoint; and receiving, by the third endpoint, apeer-to-peer response to the update message from the second endpoint,wherein the response includes information needed for the third endpointto participate in the active session with the second endpoint.
 2. Themethod of claim 1 further comprising sending, by the third endpoint, apresence message directly to the second endpoint to notify the secondendpoint that the third endpoint is online.
 3. The method of claim 2further comprising: receiving, by the third endpoint, a response to thepresence message directly from the second endpoint, wherein the responseidentifies the second endpoint as the sender of the response; anddetermining, by the third endpoint, whether the second endpointidentified in the response is the same as an endpoint identified in thesession information received from the first endpoint.
 4. The method ofclaim 1 wherein the receiving the session information includes receivingthe session information by the third endpoint directly from the firstendpoint via one of a wireline and a wireless interface.
 5. The methodof claim 1 wherein the receiving the session information includesretrieving the session information by the third endpoint from a memorylocation accessible to both the first endpoint and the third endpoint.6. The method of claim 1 wherein the session information includesSession Initiation Protocol (SIP) dialog information.
 7. The method ofclaim 6 wherein the update message is a SIP UPDATE message.
 8. Themethod of claim 1 wherein the session information includes stateinformation needed to synchronize a state machine on the third endpointwith a state machine on the second endpoint.
 9. The method of claim 1wherein the first and third endpoints are located on a single physicaldevice.
 10. A system comprising: a network interface; a processorcoupled to the network interface; and a memory coupled to the processorand containing a plurality of instructions for execution by theprocessor, the instructions including instructions for configuring athird endpoint stored at least partially in the memory to sweep anactive session existing between a first endpoint and a second endpointfrom the first endpoint to the third endpoint by: providing, by thethird endpoint, authentication credentials to an access server to gainaccess to a peer-to-peer network, wherein the access server returns aprofile containing a buddy list associated with the authenticationcredentials to the third endpoint in response, and wherein the secondendpoint is included on the buddy list as an endpoint with which thethird endpoint is authorized to communicate; identifying, by the thirdendpoint, based on the profile that the first and third endpoints aresimultaneously logged in because they gained access to the peer-to-peernetwork using identical authentication credentials; sending, by thethird endpoint, a peer-to-peer go away message directly to the firstendpoint; receiving, by the third endpoint, session information from thefirst endpoint corresponding to the session occurring between the firstand second endpoints, wherein the session information includesinformation needed by the third endpoint to participate in the sessionwith the second endpoint, and wherein the session information isreceived via peer-to-peer messaging between the first endpoint and thethird endpoint; sending, by the third endpoint, a peer-to-peer updatemessage directly to the second endpoint, wherein the update messageinstructs the second endpoint to switch the active session from thefirst endpoint to the third endpoint and includes information needed forthe second endpoint to transition the active session from the firstendpoint to the third endpoint; and receiving, by the third endpoint, apeer-to-peer response to the update message from the second endpoint,wherein the response includes information needed for the third endpointto participate in the active session with the second endpoint.
 11. Thesystem of claim 10 further comprising instructions for the firstendpoint, wherein the first endpoint is stored at least partially in thememory, the instructions including: receiving, by the first endpoint,the go away message directly from the third endpoint; checking, by thefirst endpoint, a policy associated with the first endpoint to determinean action to be taken upon receipt of the go away message; identifying,by the first endpoint, that the first endpoint is engaged in the activesession with the second endpoint; and transferring, by the firstendpoint, session information to the third endpoint, wherein the sessioninformation includes information needed by the third endpoint to enterthe active session with the second endpoint.
 12. The system of claim 11wherein the transferring the session information by the first endpointincludes storing the session information by the first endpoint in amemory location accessible to both the first endpoint and the thirdendpoint, and wherein the receiving, by the third endpoint, the sessioninformation includes retrieving the session information by the thirdendpoint from the memory location.